Photoelectric conversion element and imaging device

ABSTRACT

A photoelectric conversion element is provided and includes: an electrically conductive thin layer; an organic photoelectric conversion layer containing a compound having a partial structure represented by the following formula (I) and a fullerene or a fullerene derivative; and a transparent electrically conductive thin layer. 
                         
X represents O, S or N—R 10 , R 10  represents a hydrogen atom or a substituent, R x  and R y  represent a hydrogen atom or a substituent, with at least one representing an electron-withdrawing group, R x  and R y  may combine to form a ring, R represents a bond (—), a hydrogen atom or a substituent, with at least one being the bond, nr represents an integer of 1 to 4, R&#39;s may be the same or different when nr is 2 or more, and R&#39;s at the 2- and 3-positions or R&#39;s at the 5- and 6-positions may combine with each other to form a ring.

This application is based on and claims priority under 35 U.S.C. §119from Japanese Patent Application No. 2008-015142 filed Jan. 25, 2008,the entire disclosure of which is herein incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a photoelectric conversion element andprovides a photoelectric conversion element with high S/N and highresponse speed by specifying the materials and structures.

2. Description of Related Art

Conventional visible light sensors in general are a device fabricated byforming a photoelectric conversion site through, for example, formationof PN junction in a semiconductor such as Si. As for the solid-stateimaging device, there is widely used a flat light-receiving device wherephotoelectric conversion sites are two-dimensionally arrayed in asemiconductor to form pixels and a signal generated by photoelectricconversion in each pixel is charge-transferred and read out according toa CCD or CMOS format. The method for realizing a color solid-stateimaging device is generally fabrication of a structure where on thelight incident surface side of the flat image-receiving device, a colorfilter transmitting only light at a specific wavelength is disposed forcolor separation. In particular, a single-plate sensor in which colorfilters transmitting blue light, green light and red light,respectively, are regularly disposed on each of two-dimensionallyarrayed pixels is well known as a system widely used at present in adigital camera and the like.

In this system, since the color filter transmits only light at a limitedwavelength, untransmitted light is not utilized and the lightutilization efficiency is bad. Also, in recent years, amid the advancein fabrication of a multipixel device, the pixel size and in turn, thearea of a photodiode part become small and this brings about problems ofreduction in the aperture ratio and reduction in the light collectionefficiency.

In order to solve these problems, there may be considered a system wherephotoelectric conversion parts capable of detecting light at differentwavelengths are stacked in a longitudinal direction. As regards such asystem, for example, U.S. Pat. No. 5,965,875 discloses a sensorutilizing wavelength dependency of the absorption coefficient of Si,where a vertical stacked structure is formed and the colors areseparated by the difference in the depth, and JP-A-2003-332551 disclosesa sensor by a stacked structure using an organic photoelectricconversion layer. However, the system by the difference in the depthdirection of Si is originally disadvantageous in that the colorseparation is poor, because the absorption range is overlapped amongrespective portions and the spectroscopic property is bad. As for othermethods to solve the problems, a structure where a photoelectricconversion layer by amorphous silicon or an organic photoelectricconversion layer is formed on a signal reading substrate is known as atechnique for raising the aperture ratio.

Heretofore, several examples have been known for a photoelectricconversion element, an imaging device, a photosensor and a solar celleach using an organic photoelectric conversion layer. A highphotoelectric conversion efficiency and a low dark current are a problemin particular, and as to the improvement method in this respect, thereare disclosed, for example, introduction of a pn-junction orintroduction of a bulk-heterostructure for the former and introductionof a blocking layer for the latter.

In an attempt to raise the photoelectric conversion efficiency by theintroduction of pn-junction or bulk-heterostructure, an increase in thedark current often becomes a problem. Also, the degree of improvement inthe photoelectric conversion efficiency differs depending on thecombination of materials and in some cases, the ratio of light-signalamount/dark time noise does not increase from before introduction of thestructure above. In the case of employing the method above, whatmaterials are combined is important and in particular, when reduction inthe dark time noise is intended, this is difficult to achieve by alreadyreported combinations of materials.

Furthermore, the kind of the material used and the layer structure arenot only one of main factors for the photoelectric conversion efficiency(exciton dissociation efficiency, charge transport property) and darkcurrent (e.g., amount of dark time carrier) but also a governing factorfor the signal responsivity, though this is scarcely mentioned in pastreports.

In use as a solid-state imaging device, all of high photoelectricconversion efficiency, low dark current and high response speed need tobe satisfied, but there has not been specifically disclosed what anorganic photoelectric conversion material or a device structuresatisfies this requirement. A photoelectric conversion layer containingfullerenes is described in JP-A-2007-123707, but only by fullerenes, itis impossible to satisfy all of the above-described high photoelectricconversion efficiency, low dark current and high response speed. Also, acoating-type solar cell containing a combination of pyran and PCBM isdescribed in J. Phys. Chem. C, 111, 8661 (2007), where, however,disclosure on the dark current and high-speed response is not found andapplication or the like to a photoelectric conversion element for animaging device is neither described nor suggested.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an organicphotoelectric conversion layer exhibiting high photoelectric conversionefficiency, low dark current and high-speed responsivity, and aphotoelectric conversion element and a solid-state imaging device eachusing the layer.

In an organic photoelectric conversion element, for realizing highphotoelectric conversion efficiency, low dark current and high-speedresponsivity, the organic photoelectric conversion layer used preferablysatisfies the following requirements.

1. In terms of high efficiency and high-speed response, the signalcharge after dissociation of an exciton needs to be swiftly transmittedto both electrodes without loss. High mobility and high charge transportability with a small number of carrier trapping sites are necessary.

2. In terms of high photoelectric conversion efficiency, it is preferredthat the exciton stabilizing energy is small and the exciton can beswiftly dissociated by the effect of an externally applied electricfield or an electric field generated in the inside by pn-junction or thelike (high exciton dissociation efficiency).

3. In order to reduce as much a carrier generated in the inside at darktime as possible, it is preferred to select the intermediate level inthe inside and select a layer structure and a material that allow thepresence of less impurities working out to one of causes thereof.

4. In the case of stacking a plurality of layers, an energy levelmatching with the adjacent layer is required and if an energetic barrieris formed, this inhibits charge transport.

In the case of forming the organic photoelectric conversion layer by avapor deposition method, the decomposition temperature is preferablyhigher than the temperature allowing for vapor deposition, because thethermal decomposition during vapor deposition can be suppressed. Thecoating method is advantageous in that the layer can be formed withoutsubjecting to limitation by the decomposition above and a low cost canbe realized, but layer formation by a vapor deposition method ispreferred because uniform layer formation is easy and possible mixing ofimpurities can be reduced.

The present inventors have made intensive studies, as a result, thefollowing selection and combination of materials have been found astechniques ensuring that the requirements above are satisfied and highphotoelectric conversion efficiency, low dark current and highresponsivity can be realized.

The above-described object can be attained by the following techniques.

(1) A photoelectric conversion element comprising:

an electrically conductive thin layer,

an organic photoelectric conversion layer, and

a transparent electrically conductive thin layer,

wherein the organic photoelectric conversion layer contains a compoundhaving a partial structure represented by formula (1) and a fullerene ora fullerene derivative:

wherein X represents O, S or N—R₁₀, R₁₀ represents a hydrogen atom or asubstituent, R^(x) and R^(y) each independently represents a hydrogenatom or a substituent, with at least either one of R^(x) and R^(y)representing an electron-withdrawing group, R^(x) and R^(y) may combineto form a ring, R represents a bond, a hydrogen atom or a substituent,with at least one R being a bond (—), nr represents an integer of 1 to4, R's may be the same or different when nr is 2 or more, and R's at the2- and 3-positions or R's at the 5- and 6-positions may combine witheach other to form a ring.

(2) A photoelectric conversion element comprising:

an electrically conductive thin layer;

an organic photoelectric conversion layer; and

a transparent electrically conductive thin layer,

wherein the organic photoelectric conversion layer contains a compoundhaving a partial structure represented by formula (II) and a fullereneor a fullerene derivative:

wherein Ra, Rb and Rc each independently represents a bond or asubstituent, na, nb and nc each represents an integer of 0 to 5, Ra's,Rb's or Rc's may be the same or different when na, nb and nc each is aninteger of 2 or more, provided that na+nb+nc is not 0 and when not 0, atleast one of Ra, Rb and Rc is a bond (—), and each pair of two Ra's, twoRb's and two Rc's may combine with each other to form a ring.

(3) A photoelectric conversion element comprising:

an electrically conductive thin layer,

an organic photoelectric conversion layer, and

a transparent electrically conductive thin layer,

wherein the organic photoelectric conversion layer contains a compoundhaving partial structures represented by formulae (I) and (II) and afullerene or a fullerene derivative:

wherein X, R, R^(x), R^(y) and nr have the same meanings in (1) and Ra,Rb, Rc, na, nb and nc have the same meanings in (2).

(4) The photoelectric conversion element as described in (1) or (3),wherein X is O.

(5) The photoelectric conversion element as described in any one of (2)to (4), wherein Ra's at the 2-, 3-, 5- and 6-positions are the same,Rb's at the 2′-, 3′-, 5′- and 6′-positions are the same, and Rc's at the2″-, 3″-, 5″- and 6″-positions are the same.

(6) The photoelectric conversion element as described in (5), whereineach of the same Ra's, Rb's and Rc's is a hydrogen atom.

(7) The photoelectric conversion element as described in (5) or (6),wherein two of Ra at the 4-position, Rb at the 4′-position and Rc at the4″-position are the same.

(8) The photoelectric conversion element as described in any one of (5)to (7), wherein two of Ra at the 4-position, Rb at the 4′-position andRc at the 4″-position are a hydrogen atom.

(9) The photoelectric conversion element as described in any one of (1)to (3), wherein the compound is a compound represented by the followingformula (III):

wherein X, R^(x) and R^(y) have the same meanings as X, R^(x) and R^(y)in formula (I), respectively, R₂₁, R₂₂ and R₂₃ each independentlyrepresents a hydrogen atom or substituent, R₂₁ and R₂₂ may combine witheach other to form a ring, L₁ and L₂ each independently represents amethine group or a substituted methine group, n1 represents an integerof 1 or more, R₂₄ to R₃₇ each independently represents a hydrogen atomor a substituent, and two members out of R₂₄ to R₃₇ may combine witheach other to form a ring.

(10) The photoelectric conversion element as described in (9), whereinR₂₂ and R₂₃ both are a hydrogen atom.

(11) The photoelectric conversion element as described in (9) or (10),wherein L₁ and L₂ both are an unsubstituted methine group.

(12) The photoelectric conversion element as described in any one of (9)to (11), wherein n1 is 1.

(13) The photoelectric conversion element as described in any one of (9)to (11), wherein R₂₄ to R₃₇ each is a hydrogen atom.

(14) The photoelectric conversion element as described in any one of (9)to (13), wherein X is O.

(15) The photoelectric conversion element as described in any one of (1)to (13), wherein the fullerene is C₆₀.

(16) The photoelectric conversion element as described in any one of (1)to (15), wherein the organic photoelectric conversion layer has abulk-heterostructure formed in a state of the compound and a fullereneor a fullerene derivative being mixed.

(17) The photoelectric conversion element as described in any one of (1)to (16), wherein the ratio of a fullerene or a fullerene derivative/thecompound is 50% (by mol) or more.

(18) The photoelectric conversion element as described in any one of (1)to (17), wherein the organic photoelectric conversion layer is formed bya vacuum vapor deposition method.

(19) The photoelectric conversion element as described in any one of (1)to (17), wherein the transparent electrically conductive thin layer is asecond electrode layer and light is incident into the organicphotoelectric conversion layer from above the second electrode layer.

(20) The photoelectric conversion element as described in (19), whereinthe transparent electrically conductive thin layer comprises atransparent electrically conductive oxide.

(21) The photoelectric conversion element as described in any one of (1)to (20), wherein the transparent electrically conductive thin layer isformed directly on the organic photoelectric conversion layer.

(22) The photoelectric conversion element as described in any one of (1)to (21), wherein an electric field of 10⁻⁴ V/cm to 1×10⁷ V/cm is appliedbetween electrodes of the photoelectric conversion element.

(23) The photoelectric conversion element as described in any one of (1)to (22), wherein the electrically conductive thin layer, the organicphotoelectric conversion layer, and the transparent electricallyconductive thin layer are stacked in this order.

(24) An imaging device containing the photoelectric conversion elementdescribed in any one of (1) to (23).

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention will appear more fully upon considerationof the exemplary embodiments of the inventions, which are schematicallyset forth in the drawings, in which:

FIG. 1 is a schematic cross-sectional view showing one example of aphotoelectric conversion element having a charge-blocking layeraccording to one exemplary embodiment;

FIGS. 2A and 2B are energy diagrams showing the state of intermediatelevels in the charge-blocking layer having a two-layer structure shownin FIG. 1;

FIGS. 3A-3D are views for explaining the combination of materials forrespective layers when the charge-blocking layer shown in FIG. 1 has athree-layer structure;

FIG. 4 is a schematic cross-sectional view of a photoelectric conversionlayer having an electron-blocking layer of a three-layer structure and ahole-blocking layer of a three-layer structure;

FIG. 5 is an energy diagram for explaining how the carrier moves throughintermediate levels in the charge-blocking layer when a voltage isapplied to the photoelectric conversion element of FIG. 4;

FIG. 6 is a schematic cross-sectional view showing a rough constructionof a photoelectric conversion element according to an exemplaryembodiment;

FIG. 7 is a schematic cross-sectional view showing a modified example ofthe photoelectric conversion element in a structure shown in FIG. 6;

FIG. 8 is a schematic cross-sectional view showing a rough constructionof another example of a photoelectric conversion element according to anexemplary embodiment;

FIG. 9 is a schematic cross-sectional view showing a modified example ofthe photoelectric conversion element shown in FIG. 8;

FIG. 10 is a schematic cross-sectional view showing a rough constructionof another example of a photoelectric conversion element according to anexemplary embodiment;

FIG. 11 is a schematic cross-sectional view showing a modified exampleof the photoelectric conversion element shown in FIG. 10;

FIG. 12 is a schematic cross-sectional view of one pixel portion of asolid-state imaging device for explaining a third exemplary embodimentof the present invention;

FIG. 13 is a schematic cross-sectional view of the intermediate layershown in FIG. 12;

FIG. 14 is a schematic cross-sectional view of one pixel portion of asolid-state imaging device for explaining a fourth exemplary embodimentof the present invention;

FIG. 15 is a schematic cross-sectional view of one pixel portion of asolid-state imaging device for explaining a fifth exemplary embodimentof the present invention;

FIG. 16 is a schematic cross-sectional view of a solid-state imagingdevice for explaining a sixth exemplary embodiment of the presentinvention;

FIG. 17 is a partial schematic surface view of a solid-state imagingdevice for explaining an embodiment of the present invention;

FIG. 18 is a schematic cross-sectional view cut along the A-A line ofthe imaging device shown in FIG. 17; and

FIG. 19 is a view showing a specific construction example of the signalreadout part shown in FIG. 18,

wherein some of reference numerals and signs are set forth below.

-   200 Photoelectric conversion layer-   204 Electrode-   180 Transparent substrate-   190 Pixel electrode-   192 (192 a to 192 c) Electron-blocking layers having a three-layer    structure-   203 (203 a to 203 c) Hole-blocking layers having a three-layer    structure-   300 Counter electrode-   11 Lower electrode-   12 Photoelectric conversion layer-   13 Upper electrode

DETAILED DESCRIPTION OF THE EXEMPLARY EMBODIMENTS

According to an exemplary embodiment of the present invention, anorganic photoelectric conversion element satisfying high photoelectricconversion efficiency, low dark current and high-speed responsivity, andan imaging device containing the photoelectric conversion element can beobtained.

An exemplary embodiment of the present invention is a photoelectricconversion element having stacked therein, in order, an electricallyconductive thin layer, an organic photoelectric conversion layercomprising at least one material, and a transparent electricallyconductive thin layer,

[1] wherein the organic photoelectric conversion layer contains acompound having a partial structure represented by formula (I) and afullerene or a fullerene derivative,

[2] wherein the organic photoelectric conversion layer contains acompound having a partial structure represented by formula (II) and afullerene or a fullerene derivative, or

[3] wherein the organic photoelectric conversion layer contains acompound having partial structures represented by formulae (I) and (II)and a fullerene or a fullerene derivative.

The compound having a partial structure represented by formula (I),particularly a 4H pyran-based compound, for use in the present inventionis described in detail below.

In formula (I), X represents O, S or N—R₁₀, wherein R₁₀ represents ahydrogen atom or a substituent. R^(x) and R^(y) each independentlyrepresents a hydrogen atom or a substituent, with at least either one ofR^(x) and R^(y) representing an electron-withdrawing group, and R^(x)and R^(y) may combine to form a ring. R represents a bond, a hydrogenatom or a substituent, with at least one R being a bond (—), nrrepresents an integer of 1 to 4, and when nr is 2 or more, R's may bethe same or different. R's at the 2- and 3-positions or R's at the 5-and 6-positions may combine with each other to form a ring.

X represents an oxygen atom, a sulfur atom or N—R₁₀, and R₁₀ representsa hydrogen atom or a substituent. X is preferably an oxygen atom orN—R₁₀, more preferably an oxygen atom.

As for the substituent represented by R₁₀, the following substituent Wis be applied. Also, as for the substituent represented by R^(x) andR^(y), the following substituent W is be applied, but at least eitherone of R^(x) and R^(y) is an electron-withdrawing group. The sum totalof Sp² carbons contained in R^(x) and R^(y) is preferably 3 or more.

Examples of the substituent W include a halogen atom, an alkyl group(including a cycloalkyl group, a bicycloalkyl group and a tricycloalkylgroup), an alkenyl group (including a cycloalkenyl group and abicycloalkenyl group), an alkynyl group, an aryl group, a heterocyclicgroup (may also be called a hetero ring group), a cyano group, a hydroxygroup, a nitro group, a carboxy group, an alkoxy group, an aryloxygroup, a silyloxy group, a heterocyclic oxy group, an acyloxy group, acarbamoyloxy group, an alkoxycarbonyl group, an aryloxycarbonyl group,an amino group (including an anilino group), an ammonio group, anacylamino group, an aminocarbonylamino group, an alkoxycarbonylaminogroup, an aryloxycarbonylamino group, a sulfamoylamino group, analkylsulfonylamino group, an arylsulfonylamino group, a mercapto group,an alkylthio group, an arylthio group, a heterocyclic thio group, asulfamoyl group, a sulfo group, an alkylsulfinyl group, an arylsulfinylgroup, an alkylsulfonyl group, an arylsulfonyl group, an acyl group, anaryloxycarbonyl group, an alkoxycarbonyl group, a carbamoyl group, anarylazo group, a heterocyclic azo group, an imido group, a phosphinogroup, a phosphinyl group, a phosphinyloxy group, a phosphinylaminogroup, a phosphono group, a silyl group, a hydrazino group, a ureidogroup, a boronic acid group (—B(OH)₂), a phosphato group (—OPO(OH)₂), asulfato group (—OSO₃H) and other known substituents.

More specifically, W represents, for example, the following (1) to (48):

-   (1) a halogen atom,

such as fluorine atom, chlorine atom, bromine atom and iodine atom,

-   (2) an alkyl group,

specifically a linear, branched or cyclic, substituted or unsubstitutedalkyl group, the alkyl group including, for example, (2-a) to (2-e):

-   (2-a) an alkyl group,

preferably an alkyl group having a carbon number of 1 to 30 (e.g.,methyl, ethyl, n-propyl, isopropyl, tert-butyl, n-octyl, eicosyl,2-chloroethyl, 2-cyanoethyl, 2-ethylhexyl),

-   (2-b) a cycloalkyl group,

preferably a substituted or unsubstituted cycloalkyl group having acarbon number of 3 to 30 (e.g., cyclohexyl, cyclopentyl,4-n-dodecylcyclohexyl),

-   (2-c) a bicycloalkyl group,

preferably a substituted or unsubstituted bicycloalkyl group having acarbon number of 5 to 30 (e.g., bicyclo[1,2,2]heptan-2-yl,bicyclo[2,2,2]octan-3-yl),

-   (2-d) a tricycloalkyl group,

preferably a substituted or unsubstituted tricycloalkyl group having acarbon number of 7 to 30 (e.g., I-adamantyl), and

-   (2-e) a polycyclic cycloalkyl group having many ring structures,

here, the alkyl group in the substituent described below (for example,the alkyl group in an alkylthio group) means an alkyl group having sucha concept but also includes an alkenyl group and an alkynyl group,

-   (3) an alkenyl group,

specifically a linear, branched or cyclic, substituted or unsubstitutedalkenyl group, the alkenyl group including (3-a) to (3-c):

-   (3-a) an alkenyl group,

preferably a substituted or unsubstituted alkenyl group having a carbonnumber of 2 to 30 (e.g., vinyl, allyl, prenyl, geranyl, oleyl),

-   (3-b) a cycloalkenyl group,

preferably a substituted or unsubstituted cycloalkenyl group having acarbon number of 3 to 30 (e.g. 2-cyclopenten-1-yl, 2-cyclohexen-1-yl),and

-   (3-c) a bicycloalkenyl group,

specifically a substituted or unsubstituted bicycloalkenyl group,preferably a substituted or unsubstituted bicycloalkenyl group having acarbon number of 5 to 30 (e.g., bicyclo[2,2,1]hept-2-en-1-yl,bicyclo[2,2,2]oct-2-en-4-yl),

-   (4) an alkynyl group,

preferably a substituted or unsubstituted alkynyl group having a carbonnumber of 2 to 30 (e.g., ethynyl, propargyl, trimethylsilylethynyl),

-   (5) an aryl group,

preferably a substituted or unsubstituted aryl group having a carbonnumber of 6 to 30 (e.g., phenyl, p-tolyl, naphthyl, m-chlorophenyl,o-hexadecanoylaminophenyl, ferrocenyl),

-   (6) a heterocyclic group,

preferably a monovalent group obtained by removing one hydrogen atomfrom a 5- or 6-membered substituted or unsubstituted, aromatic ornon-aromatic heterocyclic compound, more preferably a 5- or 6-memberedaromatic heterocyclic group having a carbon number of 2 to 50 (e.g.,2-furyl, 2-thienyl, 2-pyrimidinyl, 2-benzothiazolyl; the heterocyclicgroup may also be a cationic heterocyclic group such as1-methyl-2-pyridinio and 1-methyl-2-quinolinio),

-   (7) a cyano group,-   (8) a hydroxy group,-   (9) a nitro group,-   (10) a carboxyl group,-   (11) an alkoxy group,

preferably a substituted or unsubstituted alkoxy group having a carbonnumber of 1 to 30 (e.g., methoxy, ethoxy, isopropoxy, tert-butoxy,n-octyloxy, 2-methoxyethoxy),

-   (12) an aryloxy group,

preferably a substituted or unsubstituted aryloxy group having a carbonnumber of 6 to 30 (e.g., phenoxy, 2-methylphenoxy, 4-tert-butylphenoxy,3-nitrophenoxy, 2-tetradecanoylaminophenoxy),

-   (13) a silyloxy group,

preferably a silyloxy group having a carbon number of 3 to 20 (e.g.,trimethylsilyloxy, tert-butyldimethylsilyloxy),

-   (14) a heterocyclic oxy group,

preferably a substituted or unsubstituted heterocyclic oxy group havinga carbon number of 2 to 30 (e.g., 1-phenyltetrazol-5-oxy,2-tetrahydropyranyloxy),

-   (15) an acyloxy group,

preferably a formyloxy group, a substituted or unsubstitutedalkylcarbonyloxy group having a carbon number of 2 to 30, or asubstituted or unsubstituted alkylcarbonyloxy group having a carbonnumber of 6 to 30 (e.g., formyloxy, acetyloxy, pivaloyloxy, stearoyloxy,benzoyloxy, p-methoxyphenylcarbonyloxy),

-   (16) a carbamoyloxy group,

preferably a substituted or unsubstituted carbamoyloxy group having acarbon number of 1 to 30 (e.g., N,N-dimethylcarbamoyloxy,N,N-diethylcarbamoyloxy, morpholinocarbonyloxy,N,N-di-n-octylaminocarbonyloxy, N-n-octylcarbamoyloxy),

-   (17) an alkoxycarbonyloxy group,

preferably a substituted or unsubstituted alkoxycarbonyloxy group havinga carbon number of 2 to 30 (e.g., methoxycarbonyloxy, ethoxycarbonyloxy,tert-butoxycarbonyloxy, n-octylcarbonyloxy),

-   (18) an aryloxycarbonyloxy group,

preferably a substituted or unsubstituted aryloxycarbonyloxy grouphaving a carbon number of 7 to 30 (e.g., phenoxycarbonyloxy,p-methoxyphenoxycarbonyloxy, p-n-hexadecyloxyphenoxycarbonyloxy),

-   (19) an amino group,

preferably an amino group, a substituted or unsubstituted alkylaminogroup having a carbon number of 1 to 30, a substituted or unsubstitutedanilino group having a carbon number of 6 to 30 (e.g., amino,methylamino, dimethylamino, anilino, N-methyl-anilino, diphenylamino)

-   (20) an ammonio group,

preferably an ammonio group or an ammonio group substituted by asubstituted or unsubstituted alkyl, aryl or heterocyclic group having acarbon number of 1 to 30 (e.g., trimethylammonio, triethylammonio,diphenylmethylammonio),

-   (21) an acylamino group,

preferably a formylamino group, a substituted or unsubstitutedalkylcarbonylamino group having a carbon number of 1 to 30, or asubstituted or unsubstituted arylcarbonylamino group having a carbonnumber of 6 to 30 (e.g., formylamino, acetylamino, pivaloylamino,lauroylamino, benzoylamino, 3,4,5-tri-n-octyloxyphenylcarbonylamino),

-   (22) an aminocarbonylamino group,

preferably a substituted or unsubstituted aminocarbonylamino grouphaving a carbon number of 1 to 30 (e.g., carbamoylamino,N,N-dimethylaminocarbonylamino, N,N-diethylaminocarbonylamino,morpholinocarbonylamino),

-   (23) an alkoxycarbonylamino group,

preferably a substituted or unsubstituted alkoxycarbonylamino grouphaving a carbon number of 2 to 30 (e.g., methoxycarbonylamino,ethoxycarbonylamino, tert-butoxycarbonylamino,n-octadecyloxycarbonylamino, N-methyl-methoxycarbonylamino),

-   (24) an aryloxycarbonylamino group,

preferably a substituted or unsubstituted aryloxycarbonylamino grouphaving a carbon number of 7 to 30 (e.g., phenoxycarbonylamino,p-chlorophenoxycarbonylamino, m-n-octyloxyphenoxycarbonylamino),

-   (25) a sulfamoylamino group,

preferably a substituted or unsubstituted sulfamoylamino group having acarbon number of 0 to 30 (e.g., sulfamoylamino,N,N-dimethylaminosulfonylamino, N-n-octylaminosulfonylamino),

-   (26) an alkyl- or aryl-sulfonylamino group,

preferably a substituted or unsubstituted alkylsulfonylamino grouphaving a carbon number of 1 to 30, or a substituted or unsubstitutedarylsulfonylamino group having a carbon number of 6 to 30 (e.g.,methylsulfonylamino, butylsulfonylamino, phenylsulfonylamino,2,3,5-trichlorophenylsulfonylamino, p-methylphenylsulfonylamino),

-   (27) a mercapto group,-   (28) an alkylthio group,

preferably a substituted or unsubstituted alkylthio group having acarbon number of 1 to 30 (e.g., methylthio, ethylthio, n-hexadecylthio),

-   (29) an arylthio group,

preferably a substituted or unsubstituted arylthio group having a carbonnumber of 6 to 30 (e.g., phenylthio, p-chlorophenylthio,m-methoxyphenylthio),

-   (30) a heterocyclic thio group,

preferably a substituted or unsubstituted heterocyclic thio group havinga carbon number of 2 to 30 (e.g., 2-benzothiazolylthio,I-phenyltetrazol-5-ylthio),

-   (31) a sulfamoyl group,

preferably a substituted or unsubstituted sulfamoyl group having acarbon number of 0 to 30 (e.g., N-ethylsulfamoyl,N-(3-dodecyloxypropyl)sulfamoyl, N,N-dimethylsulfamoyl,N-acetylsulfamoyl, N-benzoylsulfamoyl, N-(N′-phenylcarbamoyl)sulfamoyl),

-   (32) a sulfo group,-   (33) an alkyl- or aryl-sulfinyl group,

preferably a substituted or unsubstituted alkylsulfinyl group having acarbon number of 1 to 30, or a substituted or unsubstituted arylsulfinylgroup having a carbon number of 6 to 30 (e.g., methylsulfinyl,ethylsulfinyl, phenylsulfinyl, p-methylphenylsulfinyl),

-   (34) an alkyl- or aryl-sulfonyl group,

preferably a substituted or unsubstituted alkylsulfonyl group having acarbon number of 1 to 30, or a substituted or unsubstituted arylsulfonylgroup having a carbon number of 6 to 30 (e.g., methylsulfonyl,ethylsulfonyl, phenylsulfonyl, p-methylphenylsulfonyl),

-   (35) an acyl group,

preferably a formyl group, a substituted or unsubstituted alkylcarbonylgroup having a carbon number of 2 to 30, a substituted or unsubstitutedarylcarbonyl group having a carbon number of 7 to 30, or a substitutedor unsubstituted heterocyclic carbonyl group having a carbon number of 4to 30 and being bonded to a carbonyl group through a carbon atom (e.g.,acetyl, pivaloyl, 2-chloroacetyl, stearoyl, benzoyl,p-n-octyloxyphenylcarbonyl, 2-pyridylcarbonyl, 2-furylcarbonyl),

-   (36) an aryloxycarbonyl group,

preferably a substituted or unsubstituted aryloxycarbonyl group having acarbon number of 7 to 30 (e.g., phenoxycarbonyl,o-chlorophenoxycarbonyl, m-nitrophenoxycarbonyl,p-tert-butylphenoxycarbonyl),

-   (37) an alkoxycarbonyl group,

preferably a substituted or unsubstituted alkoxycarbonyl group having acarbon number of 2 to 30 (e.g., methoxycarbonyl, ethoxycarbonyl,tert-butoxycarbonyl, n-octadecyloxycarbonyl),

-   (38) a carbamoyl group,

preferably a substituted or unsubstituted carbamoyl group having acarbon number of 1 to 30 (e.g., carbamoyl, N-methylcarbamoyl,N,N-dimethylcarbamoyl, N,N-di-n-octylcarbamoyl,N-(methylsulfonyl)carbamoyl),

-   (39) an aryl or heterocyclic azo group,

preferably a substituted or unsubstituted arylazo group having a carbonnumber of 6 to 30, or a substituted or unsubstituted heterocyclic azogroup having a carbon number of 3 to 30 (e.g., phenylazo,p-chlorophenylazo, 5-ethylthio-1,3,4-thiadiazol-2-ylazo),

-   (40) an imido group,

preferably N-succinimido or N-phthalimido,

-   (41) a phosphino group,

preferably a substituted or unsubstituted phosphino group having acarbon number of 2 to 30 (e.g., dimethylphosphino, diphenylphosphino,methylphenoxyphosphino),

-   (42) a phosphinyl group,

preferably a substituted or unsubstituted phosphinyl group having acarbon number of 2 to 30 (e.g., phosphinyl, dioctyloxyphosphinyl,diethoxyphosphinyl),

-   (43) a phosphinyloxy group,

preferably a substituted or unsubstituted phosphinyloxy group having acarbon number of 2 to 30 (e.g., diphenoxyphosphinyloxy,dioctyloxyphosphinyloxy),

-   (44) a phosphinylamino group,

preferably a substituted or unsubstituted phosphinylamino group having acarbon number of 2 to 30 (e.g., dimethoxyphosphinylamino,dimethylaminophosphinylamino),

-   (45) a phospho group,-   (46) a silyl group,

preferably a substituted or unsubstituted silyl group having a carbonnumber of 3 to 30 (e.g., trimethylsilyl, triethylsilyl,triisopropylsilyl, tert-butyldimethylsilyl, phenyldimethylsilyl),

-   (47) a hydrazino group,

preferably a substituted or unsubstituted hydrazino group having acarbon number of 0 to 30 (e.g., trimethylhydrazino), or

-   (48) a ureido group,

preferably a substituted or unsubstituted ureido group having a carbonnumber of 0 to 30 (e.g., N,N-dimethylureido).

Also, two W's may form a ring in cooperation. The ring formed includesan aromatic or non-aromatic hydrocarbon, a heterocyclic ring, and apolycyclic condensed ring formed by the combination of these rings.Examples thereof include a benzene ring, a naphthalene ring, ananthracene ring, a phenanthrene ring, a fluorene ring, a triphenylenering, a naphthacene ring, a biphenyl ring, a pyrrole ring, a furan ring,a thiophene ring, an imidazole ring, an oxazole ring, a thiazole ring, apyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, anindolizine ring, an indole ring, a benzofuran ring, a benzothiophenering, an isobenzofuran ring, a quinolidine ring, a quinoline ring, aphthalazine ring, a naphthylidine ring, a quinoxaline ring, aquinoxazoline ring, an isoquinoline ring, a carbazole ring, aphenanthridine ring, an acridine ring, a phenanthroline ring, athianthrene ring, a chromene ring, a xanthene ring, a phenoxathiinering, a phenothiazine ring and a phenazine ring.

Among these substituents W, those having a hydrogen atom may be deprivedof the hydrogen atom and further substituted by the above-describedgroup. Examples of such a substituent include a —CONHSO₂— group(sulfonylcarbamoyl group or carbonylsulfamoyl group), a —CONHCO— group(carbonylcarbamoyl group) and an —SO₂NHSO₂— group (sulfonylsulfamoylgroup). Specific examples thereof include an alkylcarbonylaminosulfonylgroup (e.g., acetylaminosulfonyl), an arylcarbonylaminosulfonyl group(e.g., benzoylaminosulfonyl), an alkylsulfonylaminocarbonyl group (e.g.,methylsulfonylaminocarbonyl) and an arylsulfonylaminocarbonyl group(e.g., p-methylphenylsulfonylaminocarbonyl).

R represents a bond, a hydrogen atom or a substituent, and at least oneR is a bond (—), nr represents an integer of 1 to 4, and when nr is aninteger of 2 or more, R's may be the same or different. R's at the 2-and 3-positions, or R's at the 5- and 6-positions may combine with eachother to form a ring.

When R is a bond, the bond is preferably at the 2- and/or 6-positions ofthe X-containing 6-membered ring in formula (I), more preferably at the2- or 6-position. When R represents a hydrogen atom or a substituent,the hydrogen atom or substituent is preferably at the 2-, 3- or5-position of the X-containing 6-membered ring. In the case where R'sare combined to form a ring, the ring includes the same rings as thosewhich can be formed by W's above in cooperation. nr represents aninteger of 1 to 4, but nr is preferably 1 or 2. When nr is 1, R ispreferably a bond, and when nr is 2, preferably, two R's both are a bondor one is a bond, more preferably, one is a bond.

The compound having a partial structure represented by formula (I) ispreferably a compound represented by the following formula (Ia):

In the formula, X, R^(x) and R^(y) have the same meanings as X, R^(x)and R^(y) in formula (I), respectively, and the preferred ranges arealso the same. R⁷ to R⁹ each independently represents a hydrogen atom ora substituent. R⁸ and R⁹ may combine to form a ring. L represents alinking group comprising a conjugate bond. D₁ represents an atomicgroup.

R⁷ to R¹⁰ each independently represents a hydrogen atom or asubstituent. With respect to the substituent represented by R⁷ to R¹⁰,for example, those described as the substituent W may be applied.

R⁷ is preferably a hydrogen atom, an alkyl group, an aryl group, ahalogen atom or a cyano group, more preferably a hydrogen atom or analkyl group, still more preferably a hydrogen atom.

R⁸ is preferably a hydrogen atom, an alkyl group, an aryl group or aheteroaryl group or combines with R⁹ to form a ring, more preferably ahydrogen atom or an alkyl group, still more preferably a hydrogen atom.

R⁹ is preferably a hydrogen atom, an alkyl group, an alkenyl group, anaryl group or a heteroaryl group or combines with R⁸ to form a ring,more preferably an alkyl group (preferably an alkyl group having acarbon number of 2 to 20, more preferably a branched or cyclic alkylgroup having a carbon number of 3 to 20, still more preferably abranched or cyclic alkyl group having a quaternary carbon and having acarbon number of 4 to 12, yet still more preferably a tert-butyl group),an alkenyl group (preferably an alkenyl group having a carbon number of2 to 30, more preferably from 3 to 25, still more preferably from 4 to25), or an aryl group (preferably an aryl group having a substituent atthe o-position, more preferably an alkyl-substituted phenyl group havinga substituent at the o-position and having a carbon number of 7 to 30,still more preferably a 2,6-dimethyl-substituted phenyl group, yet stillmore preferably a 2,4,6-trimethylphenyl group), more preferably atert-butyl group or a 2,4,6-trimethylphenyl group, and most preferably atert-butyl group. Also, R⁹ may be -L-D₁.

X represents an oxygen atom, a sulfur atom or N—R¹⁰, and R¹⁰ representsa hydrogen atom or a substituent. X is preferably an oxygen atom orN—R¹⁰, more preferably an oxygen atom.

The substituent represented by R¹⁰ is preferably an alkyl group, analkenyl group, an alkynyl group, an aryl group, an acyl group, analkoxycarbonyl group, an aryloxycarbonyl group, a sulfamoyl group, acarbamoyl group, a sulfonyl group, a sulfinyl group or a heterocyclicgroup, more preferably an alkyl group, an alkenyl group, an alkynylgroup, an aryl group or a heterocyclic group, still more preferably analkyl group, an aryl group or an aromatic heterocyclic group, yet stillmore preferably an alkyl group or an aryl group The substituentrepresented by R¹⁰ may be further substituted. When two or moresubstituents are present, the substituents may be the same or differentand, if possible, may combine to form a ring.

L represents a linking group comprising a conjugate bond. The linkinggroup represented by L is preferably a conjugatively bonding linkinggroup formed of C, N, O, S, Se, Te, Si, Ge or the like, more preferablyan alkenylene, an alkynylene, an arylene, a divalent aromaticheterocyclic ring (preferably an aromatic heterocyclic ring formed fromazine, azole, thiophene or a furan ring), an azo, an imine or a groupcomprising N and a combination of the groups or rings above, still morepreferably an alkenylene, an arylene, a divalent aromatic heterocyclicring or a group comprising N and a combination of these groups or rings,yet still more preferably a group comprising a combination of analkenylene and an arylene having a carbon number of 6 to 30 (morepreferably a carbon number of 6 to 20, still more preferably from 6 to12).

Specific examples of the linking group represented by L are set forthbelow.

R represents a hydrogen atom, an aliphatic hydrocarbon group, an arylgroup or a heterocyclic group.

Ra and Rb each represents an aliphatic hydrocarbon group, an aryl groupor a heterocyclic group.

D₁ represents an atomic group. D₁ is preferably a group containing—NR^(a)(R^(b)), and it is more preferred that D₁ represents a divalentarylene group having bonded thereto —NR^(a)(R^(b)). R^(a) and R^(b) eachindependently represents a hydrogen atom or a substituent, and R^(a),R^(b) and L may form a ring. The substituents R^(a) and R^(b) maycombine with each other to form a ring (preferably a 5- or 6-memberedring, more preferably a 6-membered ring), and R^(a) and R^(b) each maycombine with a substituent in L to form a ring (preferably a 5- or6-membered ring, more preferably a 6-membered ring). Examples of thesubstituent represented by R^(a) and R^(b) include the above-describedsubstituent W, and above all, an aliphatic hydrocarbon group, an arylgroup and a heterocyclic group are preferred.

D₁ is preferably a divalent arylene group (preferably a phenylene group)bonded by an amino group at the para-position. The amino group may besubstituted, and the substituent of the amino group may combine with asubstituent of the aryl group (preferably a benzene ring of phenylgroup) in the arylene group. Examples of the substituent of the aminogroup include the above-described substituent W, and above all, analiphatic hydrocarbon group, an aryl group and a heterocyclic group arepreferred.

In the case where R^(a) and R^(b) each is an aliphatic hydrocarbongroup, an aryl group or a heterocyclic group, the substituent ispreferably an alkyl group, an alkenyl group, an aryl group, an alkoxygroup, an aryloxy group, an acyl group, an alkoxycarbonyl group, anaryloxycarbonyl group, an acylamino group, a sulfonylamino group, asulfonyl group, a silyl group or an aromatic heterocyclic group, morepreferably an alkyl group, an alkenyl group, an aryl group, an alkoxygroup, an aryloxy group, a silyl group or an aromatic heterocyclicgroup, still more preferably an alkyl group, an aryl group, an alkoxygroup, an aryloxy group, a silyl group or an aromatic heterocyclicgroup. As for specific examples, those described above for thesubstituent W may be applied.

R^(a) and R^(b) each is preferably an all group, an aryl group or anaromatic heterocyclic group. R¹ and R² each is preferably an alkylgroup, an alkylene group forming a ring by combining with L, or an arylgroup, more preferably an alkyl group having a carbon number of 1 to 8,an alkylene group forming a 5- or 6-membered ring by combining with L,or a substituted or unsubstituted phenyl group, still more preferably asubstituted or unsubstituted phenyl group.

The compound represented by formula (Ia) is preferably a compoundrepresented by the following formula (Ib):

wherein X, R₇ to R₉ and D₁ have the same meanings as X, R₇ to R₉ and D₁in formula (Ia), L₁ and L₂ each independently represents a methine groupor a substituted methine group, Z₁ represents an atomic group necessaryfor forming a 5- or 6-membered ring, an n represents an integer of 1 ormore. n is preferably an integer of 1 to 3.

(6) The compound represented by formula (Ib) is preferably a compoundrepresented by the following formula (Ic):

wherein X, R₇ to R₉, L₁, L₂, Z₁ and n have the same meanings as X, R₇ toR₉, L₁, L₂, Z₁ and n in formula (Ib), R₁ to R₆ each independentlyrepresents hydrogen or a substituent, and each of the pairs R₁ and R₂,R₃ and R₄, R₂ and R₅, R₄ and R₆, and R₅ and R₆ may combine to form aring.

The compound represented by formula (Ia) is preferably a compoundrepresented by the following formula (Id):

wherein R₇ to R₉, L₁, L₂, D₁ and n have the same meanings as R₇ to R₉,L₁, L₂, D₁ and n in formula (Ia), and Z₃ represents an atomic groupnecessary for forming a 5- or 6-membered ring.

The compound represented by formula (Ia) is preferably a compoundrepresented by the following formula (Ie):

wherein X, R₇ to R₉, L₁, L₂, n and D₁ have the same meaning as X, R₇ toR₉, L₁, L₂, n and D₁ in formula (Ia), and R₁₁ to R₁₄ each independentlyrepresents a hydrogen atom or a substituent.

The compound represented by formula (Ie) is preferably a compoundrepresented by the following formula (If):

wherein X, R₇ to R₁₁, R₁₄, L₁, L₂, n and D₁ have the same meaning as X,R₇ to R₁₁, R₁₄, L₁, L₂, n and D₁ in formula (Ie), and R₁₅ to R₁₈ eachindependently represents a hydrogen atom or a substituent.

It is preferred that in formula (Ie), R₁₁ to R₁₄ all are a hydrogenatom. Also, it is preferred that in formula (If), R₁₁ and R₁₄ to R₁₈ allrepresent a hydrogen atom. D₁ is preferably a group represented by thefollowing formula (Ig):

wherein R₅ and R₆ each independently represents hydrogen or asubstituent. R₅ and R₆ may combine to form a ring. It is particularlypreferred that R₅ and R₆ both are a substituted or unsubstituted phenylgroup.

The compound represented by formula (I), particularly a 4H pyran-basedcompound, for use in the present invention is described below.

In formula (I), X represents O, S or N—R₁₀, R^(x) and R^(y) eachindependently represents a hydrogen atom or a substituent, with at leasteither one of R^(x) and R^(y) representing an electron-withdrawinggroup, and R^(x) and R^(y) may combine to form a ring, provided thatR^(x) and R^(y) are not a cyano group at the same time. R₇ to R₁₀ eachindependently represents hydrogen or a substituent, and R₈ and R₉ maycombine to form a ring. L represents a linking group comprising aconjugate bond. D₁ represents an atomic group.

R^(x) and R^(y) each independently represents a hydrogen atom or asubstituent, and at least either one represents an electron-withdrawinggroup. Also, R^(x) and R^(y) may combine to form a ring. The sum totalof Sp² carbons contained in R^(x) and R^(y) is preferably 3 or more.

With respect to the substituent represented by R^(x) and R^(y), forexample, those described as the substituent W may be applied. Thesubstituent represented by R^(x) and R^(y) is preferably an alkyl group,an alkenyl group, an aryl group, an alkoxy group, an aryloxy group, acarbonyl group, a thiocarbonyl group, an oxycarbonyl group, an acylaminogroup, a carbamoyl group, a sulfonylamino group, a sulfamoyl group, asulfonyl group, a sulfinyl group, a phosphoryl group, an imino group, ahalogen atom, a silyl group or an aromatic heterocyclic group, morepreferably an electron-withdrawing group having a Hammett's σp value(for example, the definition and value of the sigma para value aredescribed in Chem. Rev., 165-195 (1991)) of 0.2 or more, still morepreferably an aryl group, an aromatic heterocyclic group, a carbonylgroup, a thiocarbonyl group, an oxycarbonyl group, a carbamoyl group, asulfamoyl group, a sulfonyl group, an imino group, a halogen atom or anelectron-withdrawing group resulting from ring formation throughcombining of R^(x) and R^(y), yet still more preferably an aromaticheterocyclic group, a carbonyl group, an imino group or anelectron-withdrawing group resulting from ring formation throughcombining of R^(x) and R^(y), and most preferably an electronwithdrawing group resulting from ring formation through combining offormed by connecting R^(x) and R^(y).

The compound represented by formula (Ib) is a compound where R^(x) andR^(y) in formula (Ia) are combined to form a ring, and in formulae (Ib)and (Ic), Z¹ represents an atomic group necessary for forming a 5- or6-membered ring. The ring formed is preferably a ring which is usuallyused as an acidic nucleus in a merocyanine dye, and specific examplesthereof include the followings:

(a) a 1,3-dicarbonyl nucleus, such as 1,3-indanedione nucleus,1,3-cyclohexanedione, 5,5-dimethyl-1,3-cyclohexanedione and1,3-dioxane-4,6-dione,

(b) a pyrazolinone nucleus, such as 1-phenyl-2-pyrazolin-5-one,3-methyl-1-phenyl-2-pyrazolin-5-one and1-(2-benzothiazoyl)-3-methyl-2-pyrazolin-5-one,

(c) an isoxazolinone nucleus, such as 3-phenyl-2-isoxazolin-5-one and3-methyl-2-isoxazolin-5-one,

(d) an oxyindole nucleus, such as 1-alkyl-2,3-dihydro-2-oxyindole,

(e) a 2,4,6-triketohexahydropyrimidine nucleus, such as barbituric acid,2-thiobarbituric acid and a derivative thereof, examples of thederivative include a 1-alkyl form such as 1-methyl and 1-ethyl, a1,3-dialkyl form such as 1,3-dimethyl, 1,3-diethyl and 1,3-dibutyl, a1,3-diaryl form such as 1,3-diphenyl, 1,3-di(p-chlorophenyl) and1,3-di(p-ethoxycarbonylphenyl), a 1-alkyl-1-aryl form such as1-ethyl-3-phenyl, and a 1,3-diheterocyclic substitution form such as1,3-di(2-pyridyl),

(f) a 2-thio-2,4-thiazolidinedione nucleus, such as rhodanine and aderivative thereof; examples of the derivative include a3-alkylrhodanine such as 3-methylrhodanine, 3-ethylrhodanine and3-allylrhodanine, a 3-arylrhodanine such as 3-phenylrhodanine, and a3-heterocyclic ring-substituted rhodanine such as3-(2-pyridyl)rhodanine,

(g) a 2-thio-2,4-oxazolidinedione (2-thio2,4-(3H,5H)-oxazoledione)nucleus, such as 3-ethyl-2-thio-2,4-oxazolidinedione,

(h) a thianaphthenone nucleus, such as3(2H)-thianaphthenone-1,1-dioxide,

(i) a 2-thio-2,5-thiazolidinedione nucleus, such as3-ethyl-2-thio-2,5-thiazolidinedione,

(j) a 2,4-thiazolidinedione nucleus, such as 2,4-thiazolidinedione,3-ethyl-2,4-thiazolidinedione and 3-phenyl-2,4-thiazolidinedione,

(k) a thiazolin-4-one nucleus, such as 4-thiazolinone and2-ethyl-4-thiazolinone,

(l) a 2,4-imidazolidinedione (hydantoin) nucleus, such as2,4-imidazolidinedione and 3-ethyl-2,4-imidazolidinedione,

(m) a 2-thio-2,4-imidazolidinedione (2-thiohydantoin) nucleus, such as2-thio-2,4-imidazolidinedione and 3-ethyl-2-thio-2,4-imidazolidinedione,

(n) an imidazolin-5-one nucleus, such as2-propylmercapto-2-imidazolin-5-one,

(o) a 3,5-pyrazolidinedione nucleus, such as1,2-diphenyl-3,5-pyrazolidinedione and1,2-dimethyl-3,5-pyrazolidinedione,

(p) a benzothiophen-3-one nucleus, such as benzothiophen-3-one,oxobenzothiophen-3-one and dioxobenzothiophen-3-one, and

(q) an indanone nucleus, such as 1-indanone, 3-phenyl-1-indanone,3-methyl-1-indanone, 3,3-diphenyl-1-indanone and3,3-dimethyl-1-indanone.

The ring formed by Z¹ is preferably a 1,3-dicarbonyl nucleus, apyrazolinone nucleus, a 2,4,6-triketohexahydropyrimidine nucleus(including a thioketone form), a 2-thio-2,4-thiazolidinedione nucleus, a2-thio-2,4-oxazolidinedione nucleus, a 2-thio-2,5-thiazolidinedionenucleus, a 2,4-thiazolidinedione nucleus, a 2,4-imidazolidinedionenucleus, a 2-thio-2,4-imidazolidinedione nucleus, a 2-imidazolin-5-onenucleus, a 3,5-pyrazolidinedione nucleus, a benzothiophen-3-one nucleusor an indanone nucleus, more preferably a 1,3-dicarbonyl nucleus, a2,4,6-triketohexahydropyrimidine nucleus (including a thioketone form),a 3,5-pyrazolidinedione nucleus, a benzothiophen-3-one nucleus or anindanone nucleus, still more preferably a 1,3-dicarbonyl nucleus or a2,4,6-triketohexahydropyrimidine nucleus (including a thioketone form),yet still more preferably a 1,3-indanedione nucleus.

L₁ and L₂ each independently represents an unsubstituted methine groupor a substituted methine group. Examples of the substituent of thesubstituted methine group include the above-described substituent W. Itis preferred that L₁ and L₂ both are an unsubstituted methine group. nrepresents an integer of 1 or more, n is preferably 1.

Also, the compound represented by formula (Ib) is preferably a compoundrepresented by formula (Ic). In the compound represented by formula(Ic), X, R₇ to R₁₀, L₁, L₂, Z₁ and n have the sane meanings as X, R₇ toR₁₀, L₁, L₂, Z₁ and n in formula (Ib), and preferred ranges are also thesame.

R₁ to R₆ each independently represents hydrogen or a substituent. Thesubstituent is preferably an aliphatic hydrocarbon group (preferably analkyl group or an alkenyl group) or an alkoxy group.

Each of the pairs R₁ and R₂, R₃ and R₄, R₂ and R₅, R₄ and R₆, and R₅ andR₆ may combine to form a ring. A case where R₂ and R₅ combine to form a6-membered ring is preferred.

The compound represented by formula (Ib) is still more preferably acompound represented by formula (Id). In formula (Id), R₇ to R₉, L₁, L₂,D₁ and n have the same meanings as R₇ to R₉, L₁, L₂, D₁ and n in formula(Ib), and preferred ranges are also the same.

Z₃ represents an atomic group necessary for forming a 5- or 6-memberedring. The ring formed by Z³ is, for example, those having a1,3-dicarbonyl structure in the ring, out of the rings formed by Z¹ informula (Ib), and examples thereof include 1,3-cyclopentanedione,1,3-cyclohexanedione, 1,3-indanedione, 3,4-pyrazolidinedione and2,4,6-triketohexahydropyrimidine nuclei. The ring is preferably a1,3-indanedione or 3,5-pyrazolidinedione nuclei, or a barbituric or2-thiobarbituric acid or a derivative thereof, more preferably1,3-indanedione or 1,2-diaryl-3,5-pyrazolidinedione, still morepreferably 1,3-indanedione or 1,2-diphenyl-3,5-pyrazolidinedione, yetstill more preferably 1,3-indanedione. The ring formed by Z³ may have asubstituent, and with respect to the substituent, for example, thosedescribed as the substituent W may be applied.

Also, the compound represented by formula (Ib) is preferably a compoundrepresented by formula (Ie). In formula (Ie), X, R₇ to R₁₀, L₁, L₂, nand D₁ have the same meanings as X, R₇ to R₁₀, L₁, L₂, n and D₁ informula (Ib), and preferred ranges are also the same.

R₁₁ to R₁₄ each independently represents a hydrogen atom or asubstituent. With respect to the substituent, for example, thosedescribed as the substituent W may be applied. A case where R₁₁ to R₁₄all are a hydrogen atom is preferred.

Also, the compound represented by formula (Ib) is preferably a compoundrepresented by formula (If). In formula (If), X, R₇ to R₁₁, R₁₄, L₁, L₂,n and D₁ have the same meanings as X, R₇ to R₁₁, R₁₄, L₁, L₂, n and D₁ nin formula (Ie), and preferred ranges are also the same.

R₁₅ to R₁₈ each independently represents a hydrogen atom or asubstituent. With respect to the substituent, for example, thosedescribed as the substituent W may be applied. A case where R₁₅ to R₁₈all are a hydrogen atom are preferred.

In formula (Ig), the substituents represented by R₅ and R₆ have the samemeanings as R^(a) and R^(b), and preferred ranges are also the same.

Specific examples of the compound represented by formula (I) are setforth below, but the present invention is not limited thereto.

The compound containing a partial structure represented by formula (II)is described in detail below.

In formula (II), Ra, Rb and Rc each independently represents a bond or asubstituent, na, nb and nc each represents an integer of 0 to 5, Ra's,Rb's or Rc's may be the same or different when na, nb and nc each is aninteger of 2 or more, provided that na+nb+nc is not 0 and when not 0, atleast one of Ra, Rb and Rc is a bond (—), and each pair of two Ra's, twoRb's and two Rc's may combine with each other to form a ring.

Ra, Rb and Rc each independently represents a bond or a substituent, andat least one of Ra, Rb and Rc is preferably a bond (—). The substitutionsite of the bond is preferably a 4-, 4′- or 4″-position. The number ofbonds in the compound is preferably 1 to 3, more preferably 1. In thecase where Ra, Rb and Rc are a substituent, examples of the substituentinclude the above-described substituent W. n a, nb and nc eachrepresents an integer of 0 to 5, and na+nb+nc is not 0 and is an integerof 1 to 15, preferably 1 to 3, more preferably 1. When na, nb and nceach is an integer of 2 or more, Ra's, Rb's or Rc's may be the same ordifferent, and each pair of two Ra's, two Rb's and two Rc's may combinewith each other to form a ring. In this case, with respect to Ra, forexample, Ra's at the 2- and 3-positions, at the 3- and 4-positions, atthe 4- and 5-positions, or at the 5- and 6-positions may combine to forman aromatic hydrocarbon ring such as benzene ring, or an aromaticheterocyclic ring. The same applies to Rb and Rc. Ra's at the 2-, 3-, 5-and 6-positions, Rb's at the 2′-, 3′-, 5′- and 6′-positions, or Rc's atthe 2″-, 3″-, 5″- and 6″-positions are preferably the same, and Ra's,Rb's or Rc's which are the same are preferably a hydrogen atom.Furthermore, two members out of Ra at the 4position, Rb at the4′-position and Rc at the 4″-position are preferably the same, and it ismore preferred that two members out of Ra at the 4-position, Rb at the4′-position and Rc at the 4″-position are a hydrogen atom.

Here, the bond (—) is preferably bonded to the bond of R in the partialstructure represented by formula (I) directly or through a linkinggroup. In this case, examples of the linking group include L₁=L₂ informula (I) and a linking group comprising a combination of L₁=L₂ and aphenylene group.

The compound containing a partial structure represented by formula (I)and a partial structure represented by formula (II) is described below.A compound containing both a partial structure represented by formula(I) and a partial structure represented by formula (II) is a preferredcompound in the present invention, and above all, a compound representedby formula (III) is preferably used.

In formula (III), X, R^(x) and R^(y) have the same meanings as X, R^(x)and R^(y) in formula (I), respectively. R₂₁, R₂₂ and R₂₃, which eachindependently represents a hydrogen atom or a substituent and in whichR₂₁ and R₂₂ may combine with each other to form a ring, have the samemeanings as R₉, R₈ and R₇ in formula (Ib), respectively, and preferredranges also the same. L₁ and L₂ each independently represents a methinegroup or a substituted methine group and n1 represents an integer of 1or more, where L₁, L₂ and n1 have the same meanings as L₁, L₂ and n informula (Ib), respectively, and preferred ranges also the same. R₂₄ toR₃₇ each independently represents a hydrogen atom or a substituent, andtwo members out of R₂₄ to R₃₇ may combine with each other to form aring. In the case where R₂₄ to R₃₇ represents a substituent, examples ofthe substituent include the above-described substituent W. In the casewhere a ring is formed by R₂₄ to R₃₇, similarly to Ra, Rb, Rc, anaromatic hydrocarbon ring such as benzene ring, or an aromaticheterocyclic ring may be formed.

The compound containing a partial structure represented by formula (I)or (II) and the compound represented by formula (III) may be synthesizedby various synthesis methods, and examples of the method which can beapplied include a method of formulating the aryl group of adi-substituted aniline skeleton and reacting it with an active methylenecompound in the absence or presence of a base. These compounds may besynthesized by referring to the methods described, for example, inJP-A-11-335661, JP-A-11-292875, JP-A-11-335368, JP-A-2000-351774,JP-A-2001-81451 and Non-Patent Document 1.

Specific examples of the compound containing a partial structurerepresented by formula (II) and the compound represented by formula(III) include D-39 to D-44 and D-104 to D-106 set forth above, but thepresent invention is not limited thereto.

The fullerene or fullerene derivative is described in detail below.

In the present invention, a photoelectric conversion element containinga fullerene or fullerene derivative in the photoelectric conversionlayer is used. The compound above may be used as any one of an organicp-type semiconductor, an organic n-type semiconductor, and an electronor hole blocking material stacked between such an organic semiconductorand an electrode, but is preferably used as an organic n-typesemiconductor.

The fullerene as referred to in the present invention indicatesfullerene C₆₀, fullerene C₇₀, fullerene C₇₆, fullerene C₇₈, fullereneC₈₀, fullerene C₈₂, fullerene C₈₄, fullerene C₉₀, fullerene C₉₆,fullerene C₂₄₀, fullerene C₅₄₀, mixed fullerene or fullerene nanotube,and the fullerene derivative indicates a compound resulting fromaddition of a substituent to the fullerene above.

In the present invention, when a specific moiety is referred to as “agroup”, this means that the moiety itself may not be substituted or maybe substituted by one or more (to a possible maximum number)substituents. For example, “an alkyl group” means a substituted orunsubstituted alkyl group. Examples of the substituent above include thesubstituent W.

The fullerene derivative for use in the present invention is preferablya fullerene derivative represented by the following formula (1).

In formula (1), R¹ represents a substituent. As for the substituent, theabove-described substituent W may be used. The substituent is preferablyan alkyl group, an aryl group or a heterocyclic group, and preferredranges and preferred specific examples thereof include those describedfor the substituent W. The alkyl group is more preferably an alkyl grouphaving a carbon number of 1 to 12, and the aryl group and heterocyclicgroup are preferably a benzene ring, a naphthalene ring, an anthracenering, a phenanthrene ring, a fluorene ring, a triphenylene ring, anaphthacene ring, a biphenyl ring, a pyrrole ring, a furan ring, athiophene ring, an imidazole ring, an oxazole ring, a thiazole ring, apyridine ring, a pyrazine ring, a pyrimidine ring, a pyridazine ring, anindolizine ring, an indole ring, a benzofuran ring, a benzothiophenering, an isobenzofuran ring, a benzimidazole ring, an imidazopyridinering, a quinolidine ring, a quinoline ring, a phthalazine ring, anaphthylidine ring, a quinoxaline ring, a quinoxazoline ring, anisoquinoline ring, a carbazole ring, a phenanthridine ring, an acridinering, a phenanthroline ring, a thianthrene ring, a chromene ring, axanthene ring, a phenoxathiine ring, a phenothiazine ring or a phenazinering, more preferably a benzene ring, a naphthalene ring, an anthracenering, a phenanthrene ring, a pyridine ring, an imidazole ring, anoxazole ring or a thiazole ring, still more preferably a benzene ring, anaphthalene ring or a pyridine ring. These each may further have asubstituent, and, if possible, the substituents may combine to form aring. Incidentally, when nf is 2 or more, the plurality of R¹'s may bethe same or different. Also, if possible, the plurality of R¹'s maycombine to form a ring.

nf represents an integer of 1 to 60 and is preferably an integer of 1 to6.

Examples of the fullerene derivative which is preferably used in thepresent invention are set forth below, but the present invention is notlimited thereto.

As for the fullerene and fullerene derivative for use in the presentinvention, the compounds described, for example, in Kikan Kagaku Sosetsu(Scientific Review Quarterly), No. 43, edited by The Chemical Society ofJapan (1999), JP-A-10-167994, JP-A-11-255508, JP-A-11-255509,JP-A-2002-241323 and JP-A-2003-196881 may also be used. The fullereneand fullerene derivative for use in the present invention can beproduced by the method or in accordance with the method described, forexample, in Kikan Kagaku Sosetsu (Scientific Review Quarterly), No. 43,edited by The Chemical Society of Japan (1999), JP-A-10-167994,JP-A-11-255508, JP-A-11-255509, JP-A-2002-241323 and JP-A-2003-196881.

It is known to increase the exciton dissociation efficiency and bringout high photoelectric conversion efficiency by joining a fullerene orfullerene derivative with another material (generally called a p-typesemiconductor) and thereby introducing a donor-acceptor interface, butthe photoelectric conversion efficiency is not expected to be greatlyincreased with all materials. By using a compound containing at leasteither one, preferably both, of the partial structures represented byformulae (I) and (II) for use in the present invention, a great increasein the photoelectric conversion efficiency becomes possible.

For introducing a sufficiently large amount of the interface, layerformation is preferably performed in a state of the compound and thefullerene or fullerene derivative for use in the present invention (thecombination of materials of the present invention) being mixed. This maybe preferably realized by co-deposition in the case of a vapordeposition method or by preparing a mixed solution and coating thesolution in the case of a coating method.

By virtue of using the combination of materials of the presentinvention, upwelling of an internal carrier, which is one of main causesof the dark current, is reduced.

For achieving high-speed responsivity, it is required that a carriertrap is not present inside of the organic photoelectric conversion layerand both an electron and a hole are smoothly transmitted. In general,the electron transport property of a normal material is poor andtherefore, high-speed response is difficult to realize for manymaterials. In the construction using the combination of materials of thepresent invention, the fullerene or fullerene derivative is excellent inthe electron transport property and by fabricating a structure where anelectron generated upon exciton separation effects the charge transportthrough a fullerene or fullerene derivative, high-speed responsivity canbe preferably realized. However, for this purpose, a structure ofallowing a fullerene or fullerene derivative to connect in thelongitudinal direction (direction toward both electrodes) of the layeris preferred. If this route is broken midway, charge transport from thefullerene (or fullerene derivative) to another material mixed (stacked)is necessary and the barrier in view of energy or physical junction hereworks as a trap and deteriorates the responsivity. In order to achievehigh-speed responsivity, a fullerene or fullerene derivative needs to beintroduced in more than a certain amount and, in terms of the amountwhen formed as a single layer layer, the amount of the fullerene orfullerene derivative is preferably 50% or more (by mol), more preferably100% or more, still more preferably 200% or more, based on the amount ofanother material forming the mixed layer.

For imparting high-speed responsivity, the material (the compoundcontaining at least either one, preferably both, of the partialstructures represented by formulae (I) and (II)) mixed with thefullerene or fullerene derivative is of course preferably a materialhaving a high electron or hole transport property as the material alone.However, the electron transport ability is compensated for by thefullerene or fullerene derivative and therefore, a material having atleast a high hole transport ability is preferred.

Usually, when an upper transparent electrode is layer-formed directly ona photoelectric conversion material layer composed of a single material,this may cause deterioration due to damage of the underlying layer,reduction in the photoelectric conversion efficiency due to badcontactability between the upper electrode and the material layer, orreduction in the response speed. For this reason and also forsuppressing an injection current from the electrode, a hole-blockinglayer (buffer layer) is provided between the upper electrode and thephotoelectric conversion layer of the present invention. However, thephotoelectric conversion layer of the present invention brings aboutstrengthening of layer resistance due to introduction of a fullerene,introduction of a large energy barrier for hole injection from fullereneand electrode, and good contactability with electrode, which isconsidered to be attributable to the spherical shape of the fullerene,and therefore, even when the hole-blocking layer (buffer layer) is notprovided, the performance in terms of photoelectric conversionefficiency, dark current, response speed and the like is notdeteriorated. Accordingly, deterioration of the response speed, which issometimes caused due to introduction of the hole-blocking layer (bufferlayer), can be structurally eliminated.

The embodiments of the present invention are described below byreferring to the drawings.

The combination of materials of the present invention is preferablycontained in the following photoelectric conversion layer, and preferredembodiments are described below with respect to the material other thanthe combination of materials of the present invention, which is used inthe photoelectric conversion layer containing the photoelectricconversion layer, the constituent element such as other layer for use inthe photoelectric conversion element containing the photoelectricconversion layer, and the imaging device containing the photoelectricconversion element.

Embodiments capable of providing a photoelectric conversion elementwhere injection of an electric charge (electron, hole) into thephotoelectric conversion layer from the electrode is suppressed and darkcurrent can be thereby effectively reduced (first to sixth embodiments)are described below.

According to these embodiments, in a photoelectric conversion elementcontaining a pair of electrodes and a photoelectric conversion layerdisposed between the pair of electrodes, when a first charge-blockinglayer for suppressing the injection of an electric charge into thephotoelectric conversion layer from one of the paired electrodes isprovided between one of the paired electrodes and the photoelectricconversion layer and the first charge-blocking layer is formed to have amultiple layer structure, dark current can be suppressed moresuccessfully than in the case of forming the first charge-blocking layerto have a single-layer structure. Also in the construction where asecond charge-blocking layer for suppressing the injection of anelectric charge into the photoelectric conversion layer from the otherof the paired electrodes is provided between the other of the pairedelectrodes and the photoelectric conversion layer, when the secondcharge-blocking layer is formed to have a multiple layer structure, darkcurrent can be suppressed more successfully than in the case of formingthe second charge-blocking layer to have a single-layer structure.Furthermore, in the case where at least two layers out of a plurality oflayers constituting each of the first charge-blocking layer and thesecond charge-blocking layer are composed of different materials, theeffect of suppressing dark current can be more enhanced. In addition, inthe case where at least two layers out of a plurality of layers are alayer composed of an inorganic material and a layer composed of anorganic material, respectively, the effect of suppressing dark currentcan be more enhanced. Specific constructions of the charge-blockinglayer are described in the following first to sixth embodiments.

First Embodiment

FIG. 1 is a schematic cross-sectional view showing one example of theconstruction of the photoelectric conversion element having acharge-blocking layer according to this embodiment.

In FIG. 1, reference numeral 200 is a photoelectric conversion layer,reference numeral 202 is a charge-blocking layer having a two-layerstructure, reference numerals 202 a and 202 b are layers constitutingthe charge-blocking layer 202, and reference numerals 201 and 204 areelectrodes.

For example, when the electrode 204 is provided as an electrode on thelight incident side, since light needs to be incident into thephotoelectric conversion layer 200, the electrode 204 is preferablycomposed of a material having high transparency. As for the electrodehaving high transparency, a transparent electrically conductive oxide(TCO) may be used. Similarly, the electrode 201 is preferably composedof a material having high transparency, because as seen in theconstruction of an imaging device described later, light needs to betransmitted beneath the electrode. Also in the case where the electrode201 is provided as an electrode on the light incident side, theelectrode 204 and the electrode 201 are preferably composed of amaterial having high transparency.

The charge-blocking layer 202 is a layer for restraining the movement ofan electric charge from the electrode 204 to the photoelectricconversion layer 200 when a voltage is applied to the electrode 201 andthe electrode 204. In the case where the charge-blocking layer 202 has asingle-layer structure, an intermediate level (e.g., impurity level) ispresent in the material itself constituting the charge-blocking layer202, and an electric charge (electron, hole) is allowed to move throughthis intermediate level to cause an increase in the dark current. Forpreventing such movement, in this embodiment, the charge-blocking layer202 is formed to have a two-layer structure but not a single-layerstructure.

It is considered that when an interface is produced between the layers202 a mid 202 b constituting the charge-blocking layer 202,discontinuity is generated in the intermediate level present in each ofthe layers 202 a and 202 b and movement of the carrier through theintermediate level or the like becomes difficult, as a result, darkcurrent can be suppressed. However, if the layers 202 a and 202 b areformed of the same material, the intermediate levels present in thelayers 202 a and 202 b may become thoroughly the same. Accordingly, formore enhancing the effect of suppressing the dark current, the materialsconstituting respective layers 202 a and 202 b are preferably different.

FIGS. 2A and 2B are energy diagrams showing the state of theintermediate level in the charge-blocking layer having a two-layerstructure shown in FIG. 1; FIG. 2A shows a case where the layers 202 aand 202 b are formed of the same material, and FIG. 2B shows a casewhere respective layers 202 a and 202 b are formed of differentmaterials.

In the case where the layers 202 a and 202 b are formed of the samematerial, as described above, an interface is produced and therefore,dark current can be suppressed as compared with a single-layerstructure. However, if the intermediate levels (S1, S2) of respectivelayers 202 a and 202 b are present at energy positions of the same levelas shown in FIG. 2A, movement of an electric charge via the intermediatelevels (shown by arrows in the Figure) of respective layers 202 a and202 b is allowed to occur.

Here, when the layers 202 a and 202 b are formed of different materials,as shown in FIG. 2B, for example, the intermediate level (S20) of thelayer 202 b is located at a higher energy position than the intermediatelevel (S10) of the layer 202 a and the difference in the energy levelworks as a barrier, so that the movement of an electric charge can beaccordingly suppressed. In this way, positions of intermediate levels inrespective layers can be unfailingly dispersed by forming two layersconstituting the charge-blocking layer 202 from different materials, asa result, the effect of suppressing the carrier movement via anintermediate level can be enhanced.

In FIG. 1, an example where the photoelectric conversion element has onecharge-blocking layer is shown, but even in the case where in FIG. 1, acharge-blocking layer for restraining movement of an electric chargefrom the electrode 201 to the photoelectric conversion layer 200 whenapplying a voltage to the electrodes 201 and 204 is provided between theelectrode 201 and the photoelectric conversion layer 200, dark currentcan be suppressed by forming the charge-blocking layer to have atwo-layer structure and furthermore, the dark current can be moresuccessfully suppressed by forming these two layers from differentmaterials.

In the above, an example where the charge-blocking layer 202 has atwo-layer structure is described, but the charge-blocking layer may havea structure consisting of three or more layers. In this case, asdescribed above, when at least two layers out of the layers constitutingthe charge-blocking layer are formed of different materials, a stepheight between intermediate levels can be unfailingly formed inside ofthe charge-blocking layer. For example, in the case of a charge-blockinglayer having a three-layer structure, a step height may be created, asshown in FIG. 3A, by forming the lowermost layer and the uppermost layerfrom a material A and forming the in-between intermediate layer from amaterial B that is different from the material A; as shown in FIG. 3B,by forming the lowermost layer from the material B and forming theintermediate and uppermost layers from the material A; as shown in FIG.3C, by forming the lowermost and intermediate layers from the material Aand forming the uppermost layer form the material B; or, as shown inFIG. 3D, by forming the lowermost layer from a material C that isdifferent from materials A and B, forming the intermediate layer fromthe material B, and forming the uppermost layer from the material A.

FIG. 4 is a schematic cross-sectional view showing another example ofthe photoelectric conversion element according to this embodiment (aphotoelectric conversion element having an electron-blocking layer witha three-layer structure and a hole-blocking layer with a three-layerstructure). FIG. 5 is an energy diagram for explaining the state ofcharge movement via intermediate levels in the electron-blocking layerand the hole-blocking layer when a voltage is applied to thephotoelectric conversion element shown in FIG. 4.

The photoelectric conversion element shown in FIG. 4 has a structurewhere a pixel electrode (transparent electrode) 190 is provided on atransparent substrate 180, an electron-blocking layer 192 with athree-layer structure (with a structure where layers 192 a to 192 c arestacked), a photoelectric conversion layer 200 and a hole-blocking layer203 (with a structure where layers 203 a to 203 c are stacked) arestacked in this order on the transparent electrode 190, and a counterelectrode 300 is further provided thereon. Out of the layers 192 a to192 c, at least two layers are formed of different materials. Here,materials of the layers 192 a to 192 c are set to be different from eachother. Similarly, out of the layers 203 a to 203 c, at least two layersare formed of different materials. Here, materials of the layers 203 ato 203 c are set to be different from each other.

By virtue of such a construction, as shown in FIG. 5, the intermediatelevels (S5, S6 and S7) of respective layers in the electron-blockinglayer 192 differ in the energy level at the application of a voltage,and a step height therebetween works as an energy barrier, as a result,an electron becomes difficult to move. Similarly, the intermediatelevels (S8, S9 and S10) of respective layers in the hole-blocking layer203 differ in the energy level, and a step height therebetween works asan energy barrier, as a result, a hole becomes difficult to move.

With respect to stacking of a plurality of layers for the blockinglayer, the effects except for the contents regarding the intermediatelevel are described below.

The above-described technique of shifting intermediate levels present inrespective layers by stacking layers enables suppressing the darkcurrent by “inhibiting transport of the injected charge”, but formationof a plurality of layers for the blocking layer also has an effect ofreducing the dark current by “suppressing injection of an electriccharge from an electrode”.

For suppressing the injection of an electric charge from an electrode,it is important “to make large the energy barrier between the electrodeand a layer adjacent thereto” and “to homogenize the blocking layer andprevent the electrode from coming into proximity to a layer below theblocking layer (a photoelectric conversion layer)”.

The former is an approach of creating an energetic injection barrier,and the latter is an approach of, in view of a physical structure,preventing an electrode material from intruding into a fine defect ofthe layer to allow proximity between the photoelectric conversion layerand the electrode and form a leak site.

When a structure composed of a plurality of layers is formed for theblocking layer, a layer adjoining an electrode out of the plurality oflayers can be set to have an energy barrier difference between the layerand the electrode, and a layer not adjoining the electrode can be set asa uniform layer having charge transport property to prevent creation ofa leak site. In this way, the functions can be divided and allocated torespective layers.

By using an inorganic material layer composed of an inorganic materialas a blocking layer adjoining an electrode and using an organic materiallayer composed of an organic material as an underlying blocking layer(between the inorganic material layer and the photoelectric conversionlayer), the dark current can be more markedly suppressed and at the sametime, reading out of a signal charge cannot be inhibited.

More specifically, in FIG. 1, the layer 202 a is formed as an inorganicmaterial layer and the layer 202 b is formed as an organic materiallayer; in FIGS. 3B and 3D, A is formed as an inorganic material layerand B is formed as an organic material layer; in FIG. 3C, B is formed asan inorganic material layer and A is formed as an organic materiallayer; or in FIG. 4, layers 192 c and 203 a are formed as inorganicmaterial layers and layers 192 a, 192 b, 203 b and 203 c are formed asorganic material layers, whereby the dark current is more significantlysuppressed and at the same time, reading out of a signal charge can beprevented from being inhibited.

As for the inorganic material constituting the inorganic material layer,it is preferred to use any of Si, Mo, Ce, Li, Hf, Ta, Al, Ti, Zn, W andZr. Also, an oxide is preferably used as the inorganic material. As forthe oxide, use of SiO is particularly preferred.

The inorganic material layer needs to have such an ionization energy Ipas to generate an energy barrier to the work function of an adjacentelectrode so as to prevent injection of an electric charge from theelectrode, and greater Ip is preferred. However, when thecharge-blocking layer is composed of this inorganic material layeralone, if the layer thickness is small, a leak site is produced betweenthe electrode and the photoelectric conversion layer and an effect ofpreventing injection is not sufficiently obtained, whereas if the layerthickness is large, charge transport property is decreased and a signalcharge can be hardly read out.

Therefore, it is important to additionally provide an organic materiallayer as an underlying layer of the inorganic material layer. Theorganic material layer is a uniform layer having charge transportproperty high enough to transport a signal charge generated in thephotoelectric conversion layer and is preferably formed of a materialwith less carriers giving rise to a dark current produced from thematerial.

By employing such a construction, a uniform and thick blocking layer canbe obtained without increasing the dark current derived from theblocking layer and decreasing the photoelectric conversion efficiency,and the dark current can be suppressed by the combinational effect withthe inorganic material layer.

The candidate for the organic material constituting the hole-blockinglayer and electron-blocking layer is described below.

(Hole Blocking Layer)

For the hole-blocking layer, an electron-accepting organic material canbe used.

Examples of the electron-accepting material which can be used include anoxadiazole derivative such as1,3-bis(4-tert-butylphenyl-1,3,4-oxadiazolyl)phenylene (OXD-7); ananthraquinodimethane derivative; a diphenylquinone derivative; abathocuproine, a bathophenanthroline and a derivative thereof, atriazole compound; a tris(8-hydroxyquinolinato)aluminum complex; abis(4-methyl-8-quinolinato)aluminum complex; a distyrylarylenederivative, and a silole compound. Also, a material having sufficientelectron transport property may be used even if it is not anelectron-accepting organic material. That is, a porphyrin-basedcompound, a styryl-based compound such as DCM(4-dicyanomethylene-2-methyl-6-(4-(dimethylaminostyryl))4H pyran), and a4H pyran-based compound can be used.

The thickness of the hole-blocking layer is preferably from 10 to 200nm, more preferably from 30 to 150 nm, still more preferably from 50 to100 nm, because if this thickness is too small, the effect ofsuppressing a dark current is decreased, whereas if it is excessivelylarge, the photoelectric conversion efficiency is reduced.

Specific examples of the candidate for the hole-blocking materialinclude the materials indicated by HB-1 to HB-5 and BCP below. In thefollowing, Ea stands for the electron affinity of the material, and Ipstands for the ionization potential of the material.

The latitude in selection of the material practically used for thehole-blocking layer is defined by the material of the adjacent electrodeand the material of the adjacent photoelectric conversion layer. Thosehaving an ionization potential (Ip) 1.3 eV or more greater than the workfunction (Wf) of the material of the adjacent electrode and having anelectron affinity (Ea) equal to or greater than Ea of the material ofthe adjacent photoelectric conversion layer are preferred.

(Electron Blocking Layer)

For the electron-blocking layer, an electron-donating organic materialcan be used. Specifically, examples of the low molecular material whichcan be used include an aromatic diamine compound such asN,N′-bis(3-methylphenyl)-(1,1′-biphenyl)-4,4′-diamine (TPD) and4,4′-bis[N-(naphthyl)-N-phenylamino]biphenyl (α-NPD), oxazole,oxadiazole, triazole, imidazole, imidazolone, a stilbene derivative, apyrazolone derivative, tetrahydroimidazole, a polyarylalkane,4,4′,4″-tris(N-(3-methylphenyl)N-phenylamino)triphenylamine (m-MTDATA),a porphyrin compound such as porphin, copper tetraphenylporphin,phthalocyanine, copper phthalocyanine and titanium phthalocyanine oxide,a triazole derivative, an oxadiazole derivative, an imidazolederivative, a polyarylalkane derivative, a pyrazoline derivative, apyrazolone derivative, a phenylenediamine derivative, an anilinederivative, an amino-substituted chalcone derivative, an oxazolederivative, a styrylanthracene derivative, a fluorenone derivative, ahydrazone derivative, and a silazane derivative. As for the polymermaterial, a polymer such as phenylenevinylene, fluorene, carbazole,indole, pyrene, pyrrole, picolin, thiophene, acetylene and diacetylene,or a derivative thereof may be used. A compound having a sufficient holetransport property may be used even if it is not an electron-donatingcompound.

The thickness of the electron-blocking layer is preferably from 10 to200 nm, more preferably from 30 to 150 nm, still more preferably from 50to 100 nm, because if this thickness is too small, the effect ofsuppressing a dark current is decreased, whereas if it is excessivelylarge, the photoelectric conversion efficiency is reduced.

Specific examples of the candidate for the electron-blocking materialinclude the materials indicated by EB-1 to EB-5, TPD and m-MTDATA below.

The latitude in selection of the material practically used in theelectron-blocking layer is defined by the material of the adjacentelectrode and the material of the adjacent photoelectric conversionlayer. Those having an electron affinity (Ea) 1.3 eV or more greaterthan the work function (Wf) of the material of the adjacent electrodeand having an ionization potential (Ip) equal to or smaller than Ip ofthe material of the adjacent photoelectric conversion layer arepreferred.

According to this embodiment, the charge-blocking layer is formed tohave a multiple layer structure without forming a conventionallyemployed single-layer charge-blocking layer, whereby injection of acarrier into the photoelectric conversion layer from the electrode whenapplying an external voltage can be suppressed and the photocurrent/darkcurrent ratio of the photoelectric conversion element can be greatlyenhanced.

Second Embodiment

In the second embodiment, a photoelectric conversion element having acharge-blocking layer with a multiple layer structure is specificallydescribed by referring to FIGS. 6 to 11.

The charge-blocking layer includes “a hole-blocking layer” working as ahigh barrier to the injection of a hole from the adjacent electrode andexhibiting a high transport ability for an electron that is aphotocurrent carrier, and “an electron-blocking layer” working as a highbarrier to the injection of an electron from the adjacent electrode andexhibiting a high transport ability for a hole that is a photocurrentcarrier. In an organic light-emitting element and the like, as describedin JP-A-11-339966 and JP-A-2002-329582, a blocking layer using anorganic material is already employed for preventing a carrier frompenetrating through a light-emitting layer, but by inserting such anorganic blocking layer between an electrode and a photoelectricconversion layer in a photoelectric conversion part, the photoelectricconversion efficiency or response speed can be enhanced withoutincurring reduction in the S/N ratio when an external voltage isapplied.

As for the material used in the hole-blocking layer, those having anionization potential not less than the work function of the material ofthe adjacent electrode and having an electron affinity not less than theelectron affinity of the material of the adjacent photoelectricconversion layer are used. As for the material used in theelectron-blocking layer, those having an electron affinity not less thanthe work function of the material of the adjacent electrode and havingan ionization potential not less than the ionization potential of thematerial of the adjacent photoelectric conversion layer are used.Specific examples thereof are the same as those described in the firstembodiment.

The structure of the photoelectric conversion element having aphotoelectric conversion part containing such a charge-blocking layer isspecifically described below.

First, the structure having a hole-blocking layer is described.

FIG. 6 is a schematic cross-sectional view showing a rough constructionof the photoelectric conversion element of this embodiment.

The photoelectric conversion element shown in FIG. 6 is configured tocontain a pair of opposing electrodes 100 and 102, and a photoelectricconversion part consisting of a photoelectric conversion layer 101composed of an organic material and formed between the electrode 100 andthe electrode 102 and a hole-blocking layer 103 formed between thephotoelectric conversion layer 101 and the electrode 100.

As shown in the Figure, the hole-blocking layer 103 has a three-layerstructure in which material layers 103 a to 103 c are stacked. Asdescribed above, at least two layers out of the material layers 103 a to103 c are preferably formed from different materials. The hole-blockinglayer 103 is sufficient if it has a multiple layer structure.

In the photoelectric conversion element shown in FIG. 6, light becomesincident from above the electrode 102 and therefore, the electrode 102serves as the electrode on the light incident side. Also, in thephotoelectric conversion element shown in FIG. 6, a voltage is appliedto the electrodes 100 and 102 so that out of electric charges (hole andelectron) generated in the photoelectric conversion layer 101, a holecan be moved to the electrode 102 and an electron can be moved to theelectrode 100 (that is, the electrode 100 is used as the electrode forelectron extraction).

As for the material of the hole-blocking layer 103, those having anionization potential not less than the work function of the material ofthe adjacent electrode 100 and having an electron affinity not less thanthe electron affinity of the material of the adjacent photoelectricconversion layer 101 are used. By providing this hole-blocking layer 103between the electrode 100 and the photoelectric conversion layer 101,not only an electron generated in the photoelectric conversion layer 101when applying a voltage to the electrodes 100 and 102 can be moved tothe electrode 100, but also injection of a hole into the photoelectricconversion layer 101 from the electrode 100 can be suppressed. Inaddition, by virtue of the three-layer structure of the hole-blockinglayer 103, the effect of suppressing the injection of a hole from theelectrode 100 into the photoelectric conversion layer 101 via anintermediate level is enhanced.

The thickness of the entire hole-blocking layer 103 is most preferablyfrom 10 to 200 nm, because an electron generated in the photoelectricconversion layer 101 needs to be moved to the electrode 100 and if thethickness above is excessively large, the external quantum efficiencydecreases, though the blocking property may be enhanced.

Also, the value obtained by dividing the voltage externally applied tothe electrodes 100 and 102 by the sum total of the thickness of thehole-blocking layer 103 and the thickness of the photoelectricconversion layer 101 (corresponding to the distance between theelectrode 100 and the electrode 102) is preferably from 1.0×10⁵ to1.0×10⁷ V/cm.

Furthermore, in the photoelectric conversion element shown in FIG. 6,light needs to be made incident into the photoelectric conversion layer101 and therefore, the electrode 102 is preferably a transparentelectrode. The term “transparent” as used herein means to transmit 80%or more of visible light at a wavelength of about 420 to about 660 nm.

In the photoelectric conversion element shown in FIG. 6, as describedlater, light needs to be transmitted to below the electrode 100 in somecases. Therefore, the electrode 100 is also preferably a transparentelectrode and the hole-blocking layer 103 is also preferablytransparent.

FIG. 7 is a schematic cross-sectional view showing a modified example ofthe photoelectric conversion element shown in FIG. 6. In thephotoelectric conversion element as shown in FIG. 6, in the case ofapplying a voltage to the electrodes 100 and 102 so that out of electriccharges (hole and electron) generated in the photoelectric conversionlayer 101, an electron can be moved to the electrode 102 and a hole canbe moved to the electrode 100 (that is, when the electrode 102 is usedas the electrode for electron extraction), there may take a constructionwhere as shown in FIG. 7, a hole-blocking layer 103 (having athree-layer structure in which material layers 103 a to 103 c arestacked) is provided between the electrode 102 and the photoelectricconversion layer 101. In this case, the hole-blocking layer 103 needs tobe transparent. By such a construction, a dark current can besuppressed.

Incidentally, by taking a construction where an inorganic material layeris disposed on the electrode interface and an organic material layer isdisposed between the inorganic material layer and the photoelectricconversion layer, for example, a construction where in FIG. 6, thematerial layer 103 c is a layer composed of an inorganic material andthe material layers 103 a and 103 b are a layer composed of an organicmaterial or where in FIG. 7, the material layer 103 a is a layercomposed of an inorganic material and the material layers 103 b and 103c are a layer composed of an organic material, as described above, thedark current can be more significantly suppressed and at the same time,reading out of a signal charge can be prevented from being inhibited.

Next, the construction having an electron-blocking layer is described.

FIG. 8 is a schematic cross-sectional view showing a rough constructionof another example (an example having an electron-blocking layer) of thephotoelectric conversion element of this embodiment. In FIG. 8, the samestructures as in FIG. 6 are indicated by the same numerals of reference.

The photoelectric conversion element shown in FIG. 8 is configured tocontain a pair of opposing electrodes 100 and 102, and a photoelectricconversion part consisting of a photoelectric conversion layer 101formed between the electrode 100 and the electrode 102 and anelectron-blocking layer 104 (having a three-layer structure in whichmaterial layers 104 a to 104 c are stacked) formed between thephotoelectric conversion layer 101 and the electrode 102. As describedabove, at least two layers out of the material layers 104 a to 104 c arepreferably composed of different materials. The electron-blocking layer104 is sufficient if it has a multiple layer structure.

In the photoelectric conversion element shown in FIG. 8, light becomesincident from above the electrode 102 and therefore, the electrode 102serves as the electrode on the light incident side. Also, in thephotoelectric conversion element shown in FIG. 8, a voltage is appliedto the electrodes 100 and 102 so that out of electric charges (hole andelectron) generated in the photoelectric conversion layer 101, a holecan be moved to the electrode 102 and an electron can be moved to theelectrode 100 (that is, the electrode 100 is used as the electrode forelectron extraction).

As for the material of the electron-blocking layer 104, those having anelectron affinity not more than the work function of the material of theadjacent electrode 102 and having an ionization potential not more thanthe ionization potential of the material of the adjacent photoelectricconversion layer 101 are used. By providing this electron-blocking layer104 between the electrode 102 and the photoelectric conversion layer101, not only a hole generated in the photoelectric conversion layer 101when applying a voltage to the electrodes 100 and 102 can be moved tothe electrode 102, but also injection of an electron into thephotoelectric conversion layer 101 from the electrode 102 can beprevented.

The thickness of die electron-blocking layer 104 is most preferably from10 to 200 nm, because a hole generated in the photoelectric conversionlayer 101 needs to be moved to the electrode 102 and if the thicknessabove is excessively large, the external quantum efficiency decreases,though the blocking property may be enhanced.

Also, the value obtained by dividing the voltage externally applied tothe electrodes 100 and 102 by the sum total of the thickness of theelectron-blocking layer 104 and the thickness of the photoelectricconversion layer 101 (corresponding to the distance between theelectrode 100 and the electrode 102) is preferably from 1.0×10⁵ to1.0×10⁷ V/cm.

Furthermore, in the photoelectric conversion element shown in FIG. 8,light needs to be made incident into the photoelectric conversion layer101 and therefore, the electrode 102 and the electron-blocking layer 104are preferably transparent.

In the photoelectric conversion element shown in FIG. 8, as describedlater, light needs to be transmitted to below the electrode 100 in somecases. Therefore, the electrode 100 is also preferably a transparentelectrode.

FIG. 9 is a schematic cross-sectional view showing a modified example ofthe photoelectric conversion element shown in FIG. 8. In thephotoelectric conversion element as shown in FIG. 8, in the case ofapplying a voltage to the electrodes 100 and 102 so that out of electriccharges (hole and electron) generated in the photoelectric conversionlayer 101, an electron can be moved to the electrode 102 and a hole canbe moved to the electrode 100 (that is, when the electrode 102 is usedas the electrode for electron extraction), there may take a constructionwhere as shown in FIG. 9, an electron-blocking layer 104 is providedbetween the electrode 100 and the photoelectric conversion layer 101. Bysuch a construction, the dark current can be suppressed.

Incidentally, by taking a construction where an inorganic material layeris disposed on the electrode interface and an organic material layer isdisposed between the inorganic material layer and the photoelectricconversion layer, for example, a construction where in FIG. 8, thematerial layer 104 a is a layer composed of an inorganic material andthe material layers 104 b and 104 c are a layer composed of an organicmaterial or where in FIG. 9, the material layer 104 c is a layercomposed of an inorganic material and the material layers 104 a and 104b are a layer composed of an organic material, as described above, thedark current can be more significantly suppressed and at the same time,reading out of a signal charge can be prevented from being inhibited.

The construction having an electron-blocking layer and a hole-blockinglayer is described below.

FIG. 10 is a schematic cross-sectional view showing a rough constructionof another example of the photoelectric conversion element (an examplehaving a photoelectric conversion part containing both anelectron-blocking layer and a hole-blocking layer) of this embodiment.In FIG. 10, the same structures as in FIGS. 6 and 8 are indicated by thesame numerals of reference.

The photoelectric conversion element shown in FIG. 10 is configured tocontain a pair of opposing electrodes 100 and 102, and a photoelectricconversion part consisting of a photoelectric conversion layer 101formed between the electrode 100 and the electrode 102, a hole-blockinglayer 103 (103 a to 103 c) formed between the photoelectric conversionlayer 101 and the electrode 100, and an electron-blocking layer 104 (104a to 104 c) formed between the photoelectric conversion layer 101 andthe electrode 102.

In the photoelectric conversion element shown in FIG. 10, light becomesincident from above the electrode 102 and therefore, the electrode 102serves as the electrode on the light incident side. Also, in thephotoelectric conversion element shown in FIG. 10, a voltage is appliedto the electrodes 100 and 102 so that out of electric charges (hole andelectron) generated in the photoelectric conversion layer 101, a holecan be moved to the electrode 102 and an electron can be moved to theelectrode 100 (that is, the electrode 100 is used as the electrode forelectron extraction).

Furthermore, the value obtained by dividing the voltage externallyapplied to the electrodes 100 and 102 by the sum total of the thicknessof the hole-blocking layer 103, the thickness of the electron-blockinglayer 104 and the thickness of the photoelectric conversion layer 101(corresponding to the distance between the electrode 100 and theelectrode 102) is preferably from 1.0×10⁵ to 1.0×10⁷ V/cm.

According to such a construction, injection of an electric charge fromboth the electrodes 100 and 102 can be restrained, and the dark currentcan be effectively suppressed.

FIG. 11 is a schematic cross-sectional view showing a modified exampleof the photoelectric conversion element shown in FIG. 10.

In the photoelectric conversion element as shown in FIG. 10, in the caseof applying a voltage to the electrodes 100 and 102 so that out ofelectric charges (hole and electron) generated in the photoelectricconversion layer 101, an electron can be moved to the electrode 102 anda hole can be moved to the electrode 100 (that is, when the electrode102 is used as the electrode for electron extraction), there may take aconstruction where as shown in FIG. 11, an electron-blocking layer 104is provided between the electrode 100 and the photoelectric conversionlayer 101 and a hole-blocking layer 103 is provided between theelectrode 102 and the photoelectric conversion layer 101.

By such a construction, injection of an electric charge from both theelectrodes 100 and 102 can be restrained, and the dark current can beeffectively suppressed.

Third Embodiment

A construction example of a solid-state imaging device using thephotoelectric conversion element having a structure shown in FIG. 11 isdescribed below. In the following, description is made by referring toFIGS. 12 to 16. In each of these Figures, similarly to theabove-described embodiments, both the hole-blocking layer and theelectron-blocking layer have a multiple layer structure. However, inFIGS. 12 to 16, for drawing convenience, each blocking layer is notillustrated in particular as being divided into a plurality of layers.

FIG. 12 is a schematic cross-sectional view of one pixel portion of asolid-state imaging device for explaining the third embodiment of thepresent invention. FIG. 13 is a schematic cross-sectional view of theintermediate layer shown in FIG. 12. In this solid-state imaging device,a large number of pixels, one of which is shown in FIG. 12, are disposedin an array manner in the same plane, and one-pixel data of the imagedata can be produced by the signal obtained from this one pixel.

One pixel of the solid-state imaging device shown in FIG. 12 isconfigured to contain an n-type silicon substrate 1, a transparentinsulating layer 7 formed on the n-type silicon substrate 1 and aphotoelectric conversion part consisting of a first electrode layer 11formed on the insulating layer 7, an intermediate layer 12 formed on thefirst electrode layer 11 and a second electrode layer 13 formed on theintermediate layer 12, where a light-shielding layer 14 having providedtherein an opening is formed on the photoelectric conversion part andthe light-receiving region of the intermediate layer 12 is limited bythe light-shielding layer 14. Also, a transparent insulating layer 15 isformed on the light-shielding layer 14 and the second electrode layer13. Incidentally, for the photoelectric conversion part formed on theinsulating layer 7, the construction of the photoelectric conversionelement described in the first or second embodiment can be employed.

As shown in FIG. 13, the intermediate layer 12 is configured such that asubbing cum electron-blocking layer 122, a photoelectric conversionlayer 123 and a hole-blocking cum buffering layer 124 are stacked inthis order on the first electrode layer 11. As described in the first orsecond embodiment, the electron-blocking layer 122 and the hole-blockingcum buffering layer 124 each is constructed by a plurality of layers.

The photoelectric conversion layer 123 is composed of a material havingsuch properties as to generate electric charges including an electronand a hole in response to light incident from above the second electrodelayer 13, render electron mobility smaller than hole mobility, andgenerate a larger number of electrons and holes in the vicinity of thesecond electrode layer 13 than in the vicinity of the first electrodelayer 11. An organic material is representative of such a material forthe photoelectric conversion layer. In the construction of FIG. 12, amaterial that absorbs green light and accordingly generates an electronand a hole is used for the photoelectric conversion layer 123. Thephotoelectric conversion layer 123 can be shared by all pixels andtherefore, this layer may be a layer in one-sheet construction and neednot be divided for each pixel.

The photoelectric conversion layer 123 can be preferably realized by thecombination of materials of the present invention. As for other organicmaterials constituting the photoelectric conversion layer 123, the layerpreferably contains at least either an organic p-type semiconductor oran organic n-type semiconductor. For each of the organic p-typesemiconductor and the n-type semiconductor, any of a quinacridonederivative, a naphthalene derivative, an anthracene derivative, aphenanthrene derivative, a tetracene derivative, a pyrene derivative, aperylene derivative and a fluoranthene derivative may be preferably usedin particular.

The organic p-type semiconductor (compound) is a donor organicsemiconductor (compound) and indicates an organic compound having aproperty of readily donating an electron, mainly typified by ahole-transporting organic compound. More specifically, this is anorganic compound having a smaller ionization potential when two organicmaterials are used in contact. Accordingly, the donor organic compoundmay be any organic compound as long as it is an organic compound havingan electron donating property. Examples of the compound which can beused include a triarylamine compound, a benzidine compound, a pyrazolinecompound, a styrlamine compound, a hydrazone compound, atriphenylmethane compound, a carbazole compound, a polysilane compound,a thiophene compound, a phthalocyanine compound, a cyanine compound, amerocyanine compound, an oxonol compound, a polyamine compound, anindole compound, a pyrrole compound, a pyrazole compound, a polyarylenecompound, a fused aromatic carbocyclic compound (e.g., naphthalenederivative, anthracene derivative, phenanthrene derivative, tetracenederivative, pyrene derivative, perylene derivative, fluoranthenederivative), and a metal complex having a nitrogen-containingheterocyclic compound as a ligand. The donor organic semiconductor isnot limited to these compounds and, as described above, any organiccompound may be used as long as its ionization potential is smaller thanthat of the organic compound used as an n-type (acceptor) compound.

The organic n-type semiconductor (compound) is an acceptor organicsemiconductor (compound) and indicates an organic compound having aproperty of readily accepting an electron, mainly typified by anelectron-transporting organic compound. More specifically, this is anorganic compound having a larger electron affinity when two organiccompounds are used in contact. Accordingly, as for the acceptor organiccompound, any organic compound can be used as long as it is an organiccompound having an electron accepting property. Examples thereof includea fused aromatic carbocyclic compound (e.g., naphthalene derivative,anthracene derivative, phenanthrene derivative, tetracene derivative,pyrene derivative, perylene derivative, fluoranthene derivative), a 5-to 7-membered heterocyclic compound containing a nitrogen atom, anoxygen atom or a sulfur atom (e.g., pyridine, pyrazine, pyrimidine,pyridazine, triazine, quinoline, quinoxaline, quinazoline, phthalazine,cinnoline, isoquinoline, pteridine, acridine, phenazine, phenanthroline,tetrazole, pyrazole, imidazole, thiazole, oxazole, indazole,benzimidazole, benzotriazole, benzoxazole, benzothiazole, carbazole,purine, triazolopyridazine, triazolopyrimidine, tetrazaindene,oxadiazole, imidazopyridine, pyralidine, pyrrolopyridine,thiadiazolopyridine, dibenzazepine, tribenzazepine), a polyarylenecompound, a fluorene compound, a cyclopentadiene compound, a silylcompound, and a metal complex having a nitrogen-containing heterocycliccompound as a ligand. The acceptor organic semiconductor is not limitedto these compounds and, as described above, any organic compound may beused as long as its electron affinity is larger than the organiccompound used as the donor organic compound.

As for the p-type organic dye or n-type organic dye, any dye may beused, but preferred examples thereof include a cyanine dye, a styryldye, a hemicyanine dye, a merocyanine dyes (including zero-methinemerocyanine (simple merocyanine)), a trinuclear merocyanine dye, atetranuclear merocyanine dye, a rhodacyanine dye, a complex cyanine dye,a complex merocyanine dye, an allopolar dye, an oxonol dye, a hemioxonoldye, a squarylium dye, a croconium dye, an azamethine dye, a coumarindye, an arylidene dye, an anthraquinone dye, a triphenylmethane dye, anazo dye, an azomethine dye, a spiro compound, a metallocene dye, afluorenone dye, a flugide dye, a perylene dye, a phenazine dye, aphenothiazine dye, a quinone dye, an indigo dye, a diphenylmethane dye,a polyene dye, an acridine dye, an acridinone dye, a diphenylamine dye,a quinacridone dye, a quinophthalone dye, a phenoxazine dye, aphthaloperylene dye, a porphyrin dye, a chlorophyll dye, aphthalocyanine dye, a metal complex dye, and a fused aromatic carboxylicdye (e.g., naphthalene derivative, anthracene derivative, phenanthrenederivative, tetracene derivative, pyrene derivative, perylenederivative, fluoranthene derivative).

The metal complex compound is described below. The metal complexcompound is a metal complex having at least one ligand containing anitrogen, oxygen or sulfur atom coordinated to a metal. The metal ion inthe metal complex is not particularly limited but is preferablyberyllium ion, magnesium ion, aluminum ion, gallium ion, zinc ion,indium ion or tin ion, more preferably beryllium ion, aluminum ion,gallium ion or zinc ion, still more preferably aluminum ion or zinc ion.As for the ligand contained in the metal complex, various ligands areknown, but examples thereof include ligands disclosed in H. Yersin,Photochemistry and Photophysics of Coordination Compounds,Springer-Verlag (1987), and Akio Yamamoto, Yuki Kinzoku Kagaku—Kiso toOyo—(Organic Metal Chemistry—Foundation and Applications—), Shokabo(1982).

The ligand is preferably a nitrogen-containing heterocyclic ligand(preferably having a carbon number of 1 to 30, more preferably from 2 to20, still more preferably from 3 to 15; which may be a monodentateligand or a bidentate or greater ligand and is preferably a bidentateligand, such as pyridine ligand, bipyridyl ligand, quinolinol ligand,hydroxyphenylazole ligand (e.g., hydroxyphenylbenzimidazole ligand,hydroxyplheniylbenzoxazole ligand, hydroxyphenylimidazole ligand)), analkoxy ligand (preferably having a carbon number of 1 to 30, morepreferably from 1 to 20, still more preferably from 1 to 10, such asmethoxy, ethoxy, butoxy and 2-ethylhexyloxy), an aryloxy ligand(preferably having a carbon number of 6 to 30, more preferably from 6 to20, still more preferably from 6 to 12, such as phenyloxy,1-naphthyloxy, 2-naphthyloxy, 2,4,6-trimethylphenyloxy and4-biphenyloxy), a heteroaryloxy ligand (preferably having a carbonnumber of 1 to 30, more preferably from 1 to 20, still more preferablyfrom 1 to 12, such as pyridyloxy, pyrazyloxy, pyrimidyloxy andquinolyloxy), an alkylthio ligand (preferably having a carbon number of1 to 30, more preferably from 1 to 20, still more preferably from 1 to12, such as methylthio and ethylthio), an arylthio ligand (preferablyhaving a carbon number of 6 to 30, more preferably from 6 to 20, stillmore preferably from 6 to 12, such as phenylthio), a heterocyclicring-substituted thio ligand (preferably having a carbon number of 1 to30, more preferably from 1 to 20, still more preferably from 1 to 12,such as pyridylthio, 2-benzimizolylthio, 2-benzoxazolylthio and2-benzothiazolylthio), or a siloxy ligand (preferably having a carbonnumber of 1 to 30, more preferably from 3 to 25, still more preferablyfrom 6 to 20, such as triphenylsiloxy group, triethoxysiloxy group andtriisopropylsiloxy group), more preferably a nitrogen-containingheterocyclic ligand, an aryloxy ligand, a heteroaryloxy ligand or asiloxy ligand, still more preferably a nitrogen-containing heterocyclicligand, an aryloxy ligand or a siloxy ligand.

The intermediate layer 12 has a p-type semiconductor layer and an n-typesemiconductor layer according to the combination of the presentinvention, and it is preferred that at least either the p-typesemiconductor or the n-type semiconductor is an organic semiconductorand a photoelectric conversion layer having a bulk heterojunctionstructural layer containing the p-type semiconductor and the n-typeconductor is provided therebetween. In this case, the bulkheterojunction structure contained in the intermediate layer 12compensates for a shortcoming that the carrier diffusion length in thephotoelectric conversion layer 123 is short, whereby the photoelectricconversion efficiency of the photoelectric conversion layer 123 can beenhanced. Incidentally, the bulk heterojunction structure is describedin detail in JP-A-2005-303266 (Japanese Patent Application No.2004-080639).

Also, the photoelectric conversion layer contained in the intermediatelayer 12 preferably has a p-type semiconductor layer and an n-typesemiconductor layer (preferably a mixed and dispersed (bulkheterojunction structure) layer), where at least either the p-typesemiconductor or the n-type semiconductor contains anorientation-controlled organic compound, more preferably where both thep-type semiconductor and the n-type semiconductor contains anorientation-controlled (controllable) organic compound. As for thisorganic compound, those having a conjugated π electron are preferablyused, and a π-electron plane aligned at an angle not perpendicular butcloser to parallel with respect to the substrate (electrode substrate)is more preferred. The angle with respect to the substrate is preferablyfrom 0 to 80°, more preferably from 0 to 60°, still more preferably from0 to 40°, yet still more preferably from 0 to 20°, even yet still morepreferably from 0 to 10°, and most preferably 0° (that is, parallel tothe substrate). Such an orientation-controlled organic compound layer issufficient if it is contained even as a part of the entire intermediatelayer 12, but the ratio of the orientation-controlled portion to theentire intermediate layer 12 is preferably 10% or more, more preferably30% or more, still more preferably 50% or more, yet still morepreferably 70% or more, even yet still more preferably 90% or more, andmost preferably 100%. In such a state, by controlling the orientation ofthe organic compound contained in the intermediate layer 12, ashortcoming that the carrier diffmsion length is short in thephotoelectric conversion layer is compensated for and the photoelectricconversion efficiency of the photoelectric conversion layer is enhanced.

In the case where the orientation of the organic compound is controlled,it is more preferred that the heterojunction plane (for example, thepn-junction plane) is not in parallel to the substrate. Theheterojunction plane is preferably aligned not in parallel but at anangle closer to perpendicular to the substrate (electrode substrate).The angle with respect to the substrate is preferably from 10 to 90°,more preferably from 30 to 90°, still more preferably from 50 to 90°,yet still more preferably from 70 to 90°, even yet still more preferablyfrom 80 to 90°, and most preferably 90° (that is, perpendicular to thesubstrate). Such an organic compound layer with the heterojunction planebeing controlled is sufficient if it is contained even as a part of theentire intermediate layer 12. The ratio of the orientation-controlledportion to the entire intermediate layer 12 is preferably 10% or more,more preferably 30% or more, still more preferably 50% or more, yetstill more preferably 70% or more, even yet still more preferably 90% ormore, and most preferably 100%. In such a case, the area of theheterojunction plane in the intermediate layer 12 and in turn the amountof the carrier produced at the interface, such as electron, hole andelectron-hole pair, can be increased and the photoelectric conversionefficiency can be enhanced. The photoelectric conversion efficiency can-be enhanced particularly in the photoelectric conversion layer where thealignments of both the heterojunction plane and the π-electron plane ofthe organic compound are controlled. These conditions are described indetail in JP-A-2006-086493 (Japanese Patent Application No.2004-079931). The thickness of the organic dye layer is preferablylarger in view of light absorption, but considering the proportion notcontributing to the electric charge separation, the thickness of theorganic dye layer is preferably from 30 to 300 nm, more preferably from50 to 250 nm, still more preferably from 80 to 200 nm.

The intermediate layer 12 containing such an organic compound islayer-formed by a dry layer-forming method or a wet layer-formingmethod. Specific examples of the dry layer-forming method include aphysical vapor-growth method such as vacuum vapor deposition,sputtering, ion plating method and MBE, and a CVD method such as plasmapolymerization. As for the wet layer-forming method, a cast method, aspin coating method, a dipping method, an LB method and the like may beused.

In the case of using a polymer compound as at least one of the p-typesemiconductor (compound) and the n-type semiconductor (compound), thelayer is preferably formed by a wet layer-forming method assured of easyproduction. In the case of using a dry layer-forming method such asvapor deposition, a polymer may decompose and therefore, can be hardlyused, but an oligomer thereof may be preferably used instead. On theother hand, in the case of using a low molecular compound, a drylayer-forming method is preferably employed, and a vacuum vapordeposition method is particularly preferred. In the vacuum vapordeposition method, basic parameters are, for example, the method ofheating the compound, such as resistance heating vapor deposition orelectron beam heating vapor deposition, the shape of the vapordeposition source, such as crucible or boat, the vacuum degree, thevapor deposition temperature, the substrate temperature, and the vapordeposition rate. In order to enable uniform vapor deposition, the vapordeposition is preferably performed while rotating the substrate. Thevacuum degree is preferably higher, and the vacuum vapor deposition isperformed at 10⁻⁴ Torr or less, preferably 10⁻⁶ Torr or less, morepreferably 10⁻⁸ Torr or less. All steps at the vapor deposition arepreferably performed in vacuum, and the compound is fundamentallyprevented from coming into direct contact with oxygen in the outside airor with water. The above-described conditions in the vacuum vapordeposition affect the crystallinity, amorphous property, density,denseness and the like of the organic layer and therefore, must bestrictly controlled. The PI or PID control of the vapor deposition rateby using a quartz oscillator and a thickness monitor such asinterferometer is preferably employed. In the case of simultaneouslyvapor-depositing two or more kinds of compounds, a co-vapor depositionmethod, a flash vapor deposition method or the like may be preferablyused.

In the photoelectric conversion layer 123 composed of an organicmaterial, when light is incident from above the second electrode 13 inthe above-described construction, an electron and a hole, which aregenerated by light absorption, are generally generated in large numberin the vicinity of the second electrode 13 and in not so large number inthe vicinity of the first electrode 11. This is ascribable to aphenomenon that light at a wavelength near the absorption peak of thephotoelectric conversion layer 123 is mostly absorbed in the vicinity ofthe second electrode 13 and the light absorption rate decreases withdistance from the vicinity of the second electrode 13. Accordingly,unless an electron or a hole generated in the vicinity of the secondelectrode 13 is efficiently moved to the silicon substrate, thephotoelectric conversion efficiency decreases, as a result, reduction inthe sensitivity of the device is incurred. Also, the signal based on thewavelength of light strongly absorbed in the vicinity of the secondelectrode 13 decreases and this incurs broadening of the width ofspectral sensitivity.

In the photoelectric conversion layer 123 composed of an organicmaterial, the electron mobility is generally very smaller than the holemobility. Furthermore, it is known that the electron mobility in thephotoelectric conversion layer 123 composed of an organic material issusceptible to oxygen and when the photoelectric conversion layer 123 isexposed to air, the electron mobility further decreases. Accordingly, inthe case of causing an electron to be moved to the silicon substrate 1,if an electron generated in the vicinity of the second electrode 13travels a long distance in the photoelectric conversion layer 123, apart of electrons are not collected at the electrode due to deactivationor the like during the travel, as a result, the sensitivity decreasesand the spectral sensitivity is broadened.

For preventing reduction in the sensitivity and broadening of thespectral sensitivity, it is effective to efficiently move an electron ora hole generated in the vicinity of the second electrode 13 to thesilicon substrate 1. In order to realize this efficient movement, themanner of managing an electron or a hole generated in the photoelectricconversion layer 123 becomes important.

The solid-state imaging device 1000 contains a photoelectric conversionlayer 123 having the above-described properties and therefore, asdescribed above, a hole is utilized by collecting it in the firstelectrode layer 11 that is an electrode opposite the electrode on thelight incident side, whereby the external quantum efficiency can beraised and enhancement of the sensitivity and sharpening of the spectralsensitivity can be achieved. Accordingly, in the solid-state imagingdevice 1000, a voltage is applied to the first electrode layer 11 andthe second electrode layer 13 so that an electron generated in thephotoelectric conversion layer 123 can be moved to the second electrodelayer 13 and a hole generated in the photoelectric conversion layer 123can be moved to the first electrode layer 11.

One function of the subbing cum electron-blocking layer 122 is toalleviate irregularities on the first electrode layer 11. In the casewhere irregularities are present on the first electrode layer 11 or adust is attached to the first electrode layer 11, when a low molecularorganic compound is vapor-deposited thereon to form a photoelectricconversion layer 123, the irregularity portion is liable to allowproduction of fine cracks in the photoelectric conversion layer 123,that is, portions where the photoelectric conversion layer 123 is formedonly as a thin layer. At this time, when the second electrode layer 13is further formed thereon, the second electrode layer 13 coverages thecrack portion and comes into proximity with the first electrode layer 11and occurrence of DC short or leak current is likely to increase. Thistendency is prominent particularly when using TCO as the secondelectrode layer 13. Accordingly, the occurrence of such a trouble can besuppressed by previously providing a subbing layer cum electron-blockinglayer 122 on the first electrode layer 11 to alleviate theirregularities.

As for the subbing layer cum electron-blocking layer 122, the matter ofimportance is to be a uniform and smooth layer. Particularly, in thecase of obtaining a smooth layer, the preferred material is an organicpolymer material such as polyaniline, polythiophene, polypyrrole,polycarbazole, PTPDES and PTPDEK, and the layer may also be formed by aspin coating method.

The electron-blocking layer 122 is provided for reducing a dark currentascribable to injection of an electron from the first electrode layer 11and blocks the injection of an electron into the photoelectricconversion layer 123 from the first electrode layer 11.

The hole-blocking cum buffering layer 125 is provided for, as ahole-blocking layer, reducing a dark current ascribable to injection ofa hole from the second electrode layer 13 and fulfills not only afunction of blocking the injection of a hole into the photoelectricconversion layer 123 from the second electrode 13 but depending on thecase, also a function of lessening a damage caused to the photoelectricconversion layer 123 during formation of the second electrode layer 13.

In the case of forming the second electrode layer 13 above thephotoelectric conversion layer 123, a high energy particle present inthe apparatus used for layer formation of the second electrode layer 13,such as, in the case of a sputtering method, sputter particle, secondaryelectron, Ar particle or oxygen anion, may collide against thephotoelectric conversion layer 123, and this may cause deterioration ofthe photoelectric conversion layer 123 and in turn, degradation of theperformance, such as increase in leak current or decrease insensitivity. One preferred method for preventing this deterioration isto provide a buffering layer 125 on the photoelectric conversion layer123.

Backing to FIG. 12, inside of the n-type silicon substrate 1, a p-typesemiconductor region (hereinafter simply referred to as “p region”) 4,an n-type semiconductor region (hereinafter simply referred to as “nregion”) 3 and a p region 2 are formed in order of increasing the depth.In the p region 4, a high-concentration p region (referred to as a p+region) 6 is formed in the surface part of the portion light-shielded bythe light-shielding layer 14, and the p+ region 6 is surrounded by an nregion 5.

The depth of the pn junction face between the p region 4 and the nregion 3 from the surface of the n-type silicon substrate 1 is set to adepth at which blue light is absorbed (about 0.2 μm). Therefore, the pregion 4 and the n region 3 form a photodiode (B photodiode) where bluelight is absorbed and a hole is accordingly generated and accumulated.The hole generated in the B photodiode is accumulated in the p region 4.

The depth of the pn junction face between the p region 2 and the n-typesilicon substrate 1 from the surface of the n-type silicon substrate 1is set to a depth at which red light is absorbed (about 2 μm).Therefore, the p region 2 and the n-type silicon substrate 1 form aphotodiode (R photodiode) where red light is absorbed and a hole isaccordingly generated and accumulated. The hole generated in the Rphotodiode is accumulated in the p region 2.

The p+ region 6 is electrically connected to the first electrode layer11 via a connection part 9 formed in the opening bored through theinsulating layer 7 and in this region, holes collected at the firstelectrode layer 11 are accumulated via the connection part 9. Theconnection part 9 is electrically insulated by an insulating layer 8from portions except for the first electrode layer 11 and the p+ region6.

The holes accumulated in the p region 2 are converted into signalsaccording to the electric charge amount by an MOS circuit comprising ap-channel MOS transistor (not shown) formed inside of the n-type siliconsubstrate 1, the holes accumulated in the p region 4 are converted intosignals according to the electric charge amount by an MOS circuitcomprising a p-channel MOS transistor (not shown) formed inside of the nregion 3, the electrons accumulated in the p+ region 6 are convertedinto signals according to the electric charge amount by an MOS circuitcomprising a p-channel channel MOS transistor (not shown) formed insideof the n region 5, and these signals are output to the outside of thesolid-state imaging device 1000. The MOS circuits above constitute thesignal readout part specified in the scope of claim for patent. Each MOScircuit is connected to a signal readout pad (not shown) by a wiring 10.Incidentally, when an extraction electrode is provided in the p region 2and p region 4 and a predetermined reset potential is applied, eachregion is depleted and the capacity of each pn junction part becomes aninfinitely small value, whereby the capacity produced on the junctionface can be made extremely small.

Such a construction enables, for example, photoelectrically converting Glight by the photoelectric conversion layer 123 and photoelectricallyconverting B light and R light by the B photodiode and R photodiode,respectively, in the n-type silicon substrate 1. Also, since G light isfirst absorbed in the upper part, excellent color separation is obtainedbetween B-G and between G-R. This is a greatly excellent point incomparison with a solid-state imaging device of the type where three PDsare stacked inside of the silicon substrate and all of BGR light areseparated inside of the silicon substrate. In the following, the portioncomposed of an inorganic material, which is formed inside of the n-typesilicon substrate 1 of the solid-state imaging device 1000 and in whichphotoelectric conversion is performed (B photodiode, R photodiode) issometimes referred to as an inorganic layer.

Incidentally, an inorganic photoelectric conversion part composed of aninorganic material, in which light transmitted thorough thephotoelectric conversion layer 123 is absorbed and an electric chargeaccording to the light is generated and accumulated, may also be formedbetween the n-type silicon substrate 1 and the first electrode layer 11(for example, between the insulating layer 7 and the n-type siliconsubstrate 1). In this case, an MOS circuit for reading out signalsaccording to electric charges accumulated in a charge accumulationregion of the inorganic photoelectric conversion part may be providedinside of the n-type silicon substrate 1 and a wiring 10 may beconnected also to this MOS circuit.

The first electrode layer 11 fulfills a role of collecting holes movedthereto after generation in the photoelectric conversion layer 123. Thefirst electrode layer 11 is divided for each pixel, whereby image datacan be produced. In the construction shown in FIG. 12, photoelectricconversion is performed also in the n-type silicon substrate 1 andtherefore, the first electrode layer 11 preferably has a visible lighttransmittance of 60% or more, more preferably 90% or more. In the caseof a construction where a photoelectric conversion region is not presentbelow the first electrode layer 11, the first electrode layer 11 mayhave low transparency. As for the material, any of ITO, IZO, ZnO₂, SnO₂,TiO₂, FTO, Al, Ag and Au may be most preferably used. Details of thefirst electrode layer 11 are described later.

The second electrode layer 13 has a function of ejecting an electronmoved thereto after generation in the photoelectric conversion layer123. The second electrode layer 13 can be used in common among allpixels. For this reason, in the solid-state imaging device 1000, thesecond electrode layer 13 is formed as a layer in one-sheetconstruction, which is shared in common among all pixels. For the secondelectrode layer 13, a material having high transparency to visible lightneeds to be used, because light must be incident into the photoelectricconversion layer 123. The second electrode layer 13 preferably has avisible light transmittance of 60% or more, more preferably 90% or more.As for the material, any of ITO, IZO, ZnO₂, SnO₂, TiO₂, FTO, Al, Ag andAu may be most preferably used. Details of the second electrode layer 13are described later.

For the inorganic layer, a pn junction or pin junction of a compoundsemiconductor such as crystalline silicon, amorphous silicon and GaAs isgenerally used. In this case, color separation is performed according tothe depth to which light intrudes into silicon, and therefore, thespectrum range detected by each of light-receiving segments stackedbecomes broad. However, color separation is significantly improved by,as shown in FIG. 12, using the photoelectric conversion layer 123 as anupper layer, that is, allowing the light transmitted through thephotoelectric conversion layer 123 to be detected in the depth directionof silicon. In particular, as shown in FIG. 12, when G light is detectedin the photoelectric conversion layer 123, light transmitted through thephotoelectric conversion layer 123 becomes B light and R light andseparation of light in the depth direction of silicon needs to be madeonly between B light and R light, as a result, color separation isimproved. Even in the case of detecting B light or R light in thephotoelectric conversion layer 123, color separation can be markedlyimproved by appropriately selecting the depth of the pn junction face insilicon.

The construction of the inorganic layer is preferably npn or pnpn fromthe light incident side. In particular, pnpn junction is more preferred,because by providing a p layer on the surface and making high thesurface potential, a hole and a dark current, which are generated in thevicinity of the surface, can be trapped and the dark current can bereduced.

Incidentally, FIG. 12 shows a construction where one layer of thephotoelectric conversion part is stacked above the n-type siliconsubstrate 1, but there may also take a construction where a plurality ofphotoelectric conversion parts are stacked above the n-type siliconsubstrate 1. The construction where a plurality of photoelectricconversion parts are stacked is described in later embodiments. In thecase of such a construction, light detected in the inorganic layer maybe light of only one color, and preferred color separation can beachieved. Also, in the case of detecting lights of four colors by onepixel of the solid-state imaging device 1000, there may be considered,for example, a construction where one color is detected in onephotoelectric conversion part and three colors are detected in theinorganic layer; a construction where two layers of the photoelectricconversion part are stacked to detect two colors and other two colorsare detected in the inorganic layer; and a construction where threelayers of the photoelectric conversion part are stacked to detect threecolors and other one color is detected in the inorganic layer.Furthermore, the solid-state imaging device 1000 may also take aconstruction where only one color is detected by one pixel. This is aconstruction where in FIG. 1, the p region 2, the n region 3 and the pregion 4 are eliminated.

The inorganic layer is described in more detail. The preferredconstruction of the inorganic layer includes a light-receiving device ofphotoconductive type, p-n junction type, Schottky junction type, PINjunction type or MSM (metal-semiconductor-metal) type, and aphototransistor type light-receiving device. In particular, it ispreferred to use an inorganic layer where as shown in FIG. 12, aplurality of regions of first conductivity type and a plurality ofregions of second conductivity type which is a conductivity typeopposite the first conductivity type are alternately stacked inside of asingle semiconductor substrate and the junction planes each betweenregions of first conductivity type and second conductivity type areformed at respective depths suitable for photoelectrically convertingmainly lights in a plurality of different wavelength bands. The singlesemiconductor substrate is preferably single-crystal silicon, and colorseparation can be effected by utilizing the absorption wavelengthproperty dependent on the depth direction of the silicon substrate.

The inorganic semiconductor may also be an InGaN-based, InAlN-based,InAlP-based or InGaAlP-based inorganic semiconductor. The InGaN-basedinorganic semiconductor is an inorganic semiconductor adjusted to have amaximum absorption value in the blue wavelength range by appropriatelychanging the composition of In content. That is, the composition becomesIn_(x)Ga_(1−x)N (0≦x<1). Such a compound semiconductor is produced byusing a metal organic chemical vapor deposition method (MOCVD method).The InAlN-based nitride semiconductor using Al which is the same Group13 raw material as Ga may also be used as a short wavelengthlight-receiving part, similarly to the InGaN-based semiconductor.Furthermore, the InAlP or InGaAlP that lattice-matches with a GaAssubstrate may also be used.

The inorganic semiconductor may be of a buried structure. The “buriedstructure” indicates a construction where both ends of a shortwavelength light-receiving part are covered by a semiconductor differentfrom the short wavelength light-receiving part. The semiconductor forcovering both ends is preferably a semiconductor having a band gapwavelength shorter than or equal to the band gap wavelength of the shortwavelength light-receiving part.

As for the material of the first electrode layer 11 and the secondelectrode layer 13, a metal, an alloy, a metal oxide, an electricconducting compound or a mixture thereof may be used. The metal materialincludes an arbitrary combination of elements selected from Li, Na, Mg,K, Ca, Rb, Sr, Cs, Ba, Fr, Ra, Sc, Ti, Y, Zr, Hf, V, Nb, Ta, Cr, Mo, W,Mn, Tc, Re, Fe, Ru, Os, Co, Rh, Ir, Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, Al,Ga, In, Tl, Si, Ge, Sn, Pb, P, As, Sb, Bi, Se, Te, Po, Br, I, At, B, C,N, F, O and S. Among these, preferred are Al, Pt, W, Au, Ag, Ta, Cu, Cr,Mo, Ti, Ni, Pd and Zn.

The first electrode layer 11 extracts and collects holes from ahole-transporting photoelectric conversion layer or hole transport layercontained in the intermediate layer 12 and therefore, the material isselected by taking into consideration the adherence to adjacent layerssuch as hole-transporting photoelectric conversion layer and holetransport layer, the electron affinity, the ionization potential, thestability and the like. The second electrode layer 13 extracts andejects electrons from an electron-transporting photoelectric conversionlayer or electron transport layer contained in the intermediate layer 12and therefore, the material is selected by taking into consideration theadherence to adjacent layers such as electron-transporting photoelectricconversion layer and electron transport layer, the electron affinity,the ionization potential, the stability and the like. Specific examplesthereof include an electrically conductive metal oxide such as tinoxide, zinc oxide, indium oxide and indium tin oxide (ITO), a metal suchas gold, silver, chromium and nickel, a mixture or laminate of such ametal and such an electrically conductive metal oxide, an inorganicelectrically conductive substance such as copper iodide and coppersulfide, an organic electrically conductive material such aspolyaniline, polythiophene and polypyrrole, a silicon compound, and alaminate thereof with ITO. Among these, an electrically conductive metaloxide is preferred, and ITO and IZO are more preferred in view ofproductivity, high electrical conductivity, transparency and the like.

For the production of the electrode, various methods are used accordingto the material, but, for example, in the case of ITO, the layer isformed by a method such as electron beam method, sputtering method,resistance heating vapor deposition method, chemical reaction method(e.g., sol-gel method) or coating of a dispersion of indium tin oxide.In the case of ITO, an UV-ozone treatment, a plasma treatment or thelike can be applied.

The conditions when forming an electrode layer that is transparent(transparent electrode layer) are described below. The silicon substratetemperature when forming the transparent electrode layer is preferably500° C. or less, more preferably 300° C. or less, still more preferably200° C. or less, yet still more preferably 150° C. or less. A gas may beintroduced during the formation of the transparent electrode layer, andthe gas species is basically not limited, but Ar, He, oxygen or nitrogenmay be used. Also, a mixed gas of these gases may be used. Inparticular, in the case where the material is an oxide, an oxygen defectenters the layer in many cases and therefore, oxygen is preferably used.

The preferred range of the surface resistance of the transparentelectrode layer varies depending on whether the layer is the firstelectrode layer 11 or the second electrode layer 13. In the case wherethe signal readout part is in a CMOS structure, the surface resistanceof the transparent conductive layer is preferably 10,000 Ω/sq. or less,more preferably 1,000 Ω/sq. or less. In the case where the signalreadout part is hypothetically in a CCD structure, the surfaceresistance is preferably 1,000 Ω/sq. or less, more preferably 100 Ω/sq.or less, In use as the second electrode layer 13, the surface resistanceis preferably 1,000,000 Ω/sq. or less, more preferably 100,000 Ω/sq. orless.

The material of the transparent electrode layer is preferably anymaterial of ITO, IZO, SnO₂, ATO (antimony-doped tin oxide), ZnO, AZO(Al-doped zinc oxide), GZO (gallium-doped zinc oxide), TiO₂ and FTO(fluorine-doped tin oxide). The light transmittance of the transparentelectrode layer is preferably 60% or more, more preferably 80% or more,still more preferably 90% or more, yet still more preferably 95% ormore, at the absorption peak wavelength of a photoelectric conversionlayer contained in the photoelectric conversion part containing thetransparent electrode layer.

In the case of stacking a plurality of intermediate layers 12, the firstelectrode layer 11 and the second electrode layer 13 each needs totransmit light at wavelengths other than light detected by respectivephotoelectric conversion layers from the photoelectric conversion layerpositioned nearest to the light incident side to the photoelectricconversion layer positioned farthest from the light incident andtherefore, it is preferred to use a material having a lighttransmittance of preferably 90%, more preferably at least 95% or more,for visible light.

The second electrode layer 13 is preferably produced in a plasma-freestate. By producing the second electrode layer 13 in a plasma-freestate, the effect of a plasma on the substrate can be reduced and goodphotoelectric conversion properties can be obtained. Here, the term“plasma-free state” means a state where a plasma is not generated duringformation of the second electrode layer 13 or where the distance fromthe plasma generation source to the substrate is 2 cm or more,preferably 10 cm or more, more preferably 20 cm or more, and the plasmathat reaches the substrate is reduced.

Examples of the apparatus where a plasma is not generated duringformation of the second electrode layer 13 include an electron beamvapor deposition apparatus (EB vapor deposition apparatus) and a pulselaser vapor deposition apparatus. As for the EB vapor depositionapparatus and pulse laser vapor deposition apparatus, there may be usedan apparatus described, for example, in Yutaka Sawada (supervisor),Toumei Doden Maku no Shin Tenkai (New Development of TransparentElectrically Conductive Layer), CMC (1999), Yutaka Sawada (supervisor),Toumei Doden Maku no Shin Tenkai II (New Development II of TransparentElectrically Conductive Layer), CMC (2002), Toumei Doden Maku no Gijutsu(Technology of Transparent Electrically Conductive Layer), JSPS, Ohmsha(1999), and references and the like recited therein. In the following,the method of performing the formation of transparent electrode layer byusing an EB vapor deposition apparatus is referred to as an “EB vapordeposition method”, and the method of performing the formation oftransparent electrode layer by using a pulse laser vapor depositionapparatus is referred to as a “pulse laser vapor deposition method”.

As for the apparatus capable of realizing a state where the distancefrom the plasma generation source to the substrate is 2 cm or more andthe plasma that reaches the substrate is reduced (hereinafter referredto as a “plasma-free layer-forming apparatus”), for example, a countertarget-type sputtering apparatus and an arc plasma vapor depositionmethod may be used. In this regard, there may be used an apparatusdescribed, for example, in Yutaka Sawada (supervisor), Toumei Doden Makuno Shin Tenkai (New Development of Transparent Electrically ConductiveLayer), CMC (1999), Yutaka Sawada (supervisor), Toumei Doden Maku noShin Tenkai II (New Development II of Transparent ElectricallyConductive Layer), CMC (2002), Toumei Doden Maku no Gijutsu (Technologyof Transparent Electrically Conductive Layer), JSPS, Ohmsha (1999), andreferences and the like recited therein.

In the case where the second electrode layer 13 is a transparentelectrically conductive layer such as TCO, occurrence of DC short orleak current sometimes increases. One of causes thereof is consideredbecause fine cracks introduced into the photoelectric conversion layer123 are coveraged by a dense layer such as TCO, and conduction with thefirst electrode layer 11 on the opposite side increases. Therefore, inthe case of an electrode having relatively poor layer quality such asAl, the leak current less increases. The increase of leak current can begreatly suppressed by controlling the thickness of the second electrodelayer 13 with respect to the thickness (that is, the crack depth) of thephotoelectric conversion layer 123. The thickness of the secondelectrode layer 13 is preferably ⅕ or less, more preferably 1/10 orless, of the thickness of the photoelectric conversion layer 123.

Usually, when the thickness of the electrically conductive layer is madesmaller than a certain range, an abrupt increase of the resistance valueis brought about, but in the solid-state imaging device 1000 of thisembodiment, the sheet resistance may be preferably from 100 to 10,000Ω/sq. and the latitude as to in which range the layer thickness can bereduced is large. Also, as the thickness of the transparent electricallyconductive thin layer is smaller, the quantity of light absorbed becomessmall and the light transmittance generally increases. The increase oflight transmittance brings about an increase of light absorption in thephotoelectric conversion layer 123 and an increase of photoelectricconversion performance, and this is very preferred. Considering thesuppression of leak current as well as the increase of resistance valueof thin layer and increase of transmittance, which are associated withreduction in the layer thickness, the thickness of the transparentelectrically conductive thin layer is preferably from 5 to 100 nm, morepreferably from 5 to 20 nm.

The material of the transparent electrode layer is preferably a materialwhich can be layer-formed by a plasma-free layer-forming apparatus, anEB vapor deposition apparatus or a pulsed laser vapor depositionapparatus, and suitable examples thereof include a metal, an alloy, ametal oxide, a metal nitride, a metal boride, an organic electricallyconductive compound and a mixture thereof. Specific examples thereofinclude an electrically conductive metal oxide such as tin oxide, zincoxide, indium oxide, indium zinc oxide (IZO), indium tin oxide (ITO) andindium tungsten oxide (IWO), a metal nitride such as titanium nitride, ametal such as gold, platinum, silver, chromium, nickel and aluminum, amixture or laminate of such a metal and such an electrically conductivemetal oxide, an inorganic electrically conductive substance such ascopper iodide and copper sulfide, an organic electrically conductivematerial such as polyaniline, polythiophene and polypyrrole, and alaminate thereof with ITO. Furthermore, those described in detail, forexample in Yutaka Sawada (supervisor), Toumei Doden Maku no Shin Tenkai(New Development of Transparent Conductive Layer), CMC (1999), YutakaSawada (supervisor), Toumei Doden Maku no Shin Tenkai II (NewDevelopment II of Transparent Conductive Layer), CMC (2002), and ToumeiDoden Maku no Gijutsu (Technology of Transparent Conductive Layer),JSPS, Ohmsha (1999) may be also used.

Fourth Embodiment

In this embodiment, the inorganic layer having a construction shown inFIG. 12 described in the third embodiment is configured such that twophotodiodes are not stacked inside of the n-type silicon substrate buttwo diodes are arrayed in the direction perpendicular to the incidencedirection of incident light to detect light of two colors inside then-type silicon substrate.

FIG. 14 is a schematic cross-sectional view of one pixel portion of asolid-state imaging device for explaining the fourth embodiment of theinvention.

One pixel of the solid-state imaging device 2000 shown in FIG. 14 isconfigured to contain an n-type silicon substrate 17 and a photoelectricconversion part consisting of a first electrode layer 30 formed abovethe a-type silicon substrate 17, an intermediate layer 31 formed on thefirst electrode layer 30 and a second electrode layer 32 formed on theintermediate layer 31, where a light-shielding layer 34 having providedtherein an opening is formed on the photoelectric conversion part andthe light-receiving region of the intermediate layer 31 is limited bythe light-shielding layer 34. Also, a transparent insulating layer 33 isformed on the light-shielding layer 34.

The first electrode layer 30, the intermediate layer 31 and the secondelectrode layer 32 have the same constructions as the first electrodelayer 11, the intermediate layer 12 and the second electrode layer 13,respectively.

On the surface of the n-type silicon substrate 17 below the opening ofthe light-shielding layer 34, a photodiode consisting of an n region 19and a p region 18 and a photodiode consisting of an n region 21 and a pregion 20 are formed to be juxtaposed on the surface of the n-typesilicon substrate 17. An arbitrary direction on the n-type siliconsubstrate 17 surface comes under the direction perpendicular to theincidence direction of incident light.

Above the photodiode consisting of an n region 19 and a p region 18, acolor filter 28 that transmits B light is formed via a transparentinsulating layer 24, and the first electrode layer 30 is formed thereon.Above the photodiode consisting of an n region 21 and a p region 20, acolor filter 29 that transmits R light is formed via the transparentinsulating layer 24, and the first electrode layer 30 is formed thereon.The peripheries of color filters 28 and 29 are covered with atransparent insulating layer 25.

The photodiode consisting of an n region 19 and a p region 18 absorbs Blight transmitted through the color filter 28, generates holes accordingto the light absorbed and accumulates the generated holes in the pregion 18. The photodiode consisting of an n region 21 and a p region 20absorbs R light transmitted through the color filter 29, generates holesaccording to the light absorbed and accumulates the generated holes inthe p region 20.

In the portion light-shielded by the light-shielding layer 34 on thep-type silicon substrate 17 surface, a p+ region 23 is formed, and theperiphery of the p+ region 23 is surrounded by an n region 22.

The p+ region 23 is electrically connected to the first electrode layer30 via a connection part 27 formed in the opening bored through theinsulating layers 24 and 25 and in this region, holes collected at thefirst electrode layer 30 are accumulated via the connection part 27. Theconnection part 27 is electrically insulated by an insulating layer 26from portions except for the first electrode layer 30 and the p+ region23.

The holes accumulated in the p region 18 are converted into signalsaccording to the electric charge amount by an MOS circuit comprising ap-channel MOS transistor (not shown) formed inside of the n-type siliconsubstrate 17, the holes accumulated in the p region 20 are convertedinto signals according to the electric charge amount by an MOS circuitcomprising a p-channel MOS transistor (not shown) formed inside of then-type silicon substrate 17, the holes accumulated in the p+ region 23are converted into signals according to the electric charge amount by anMOS circuit comprising a p-channel MOS transistor (not shown) formedinside of the n region 22, and these signals are output to the outsideof the solid-state imaging device 2000. The MOS circuits aboveconstitute the signal readout part specified in the scope of claim forpatent. Each MOS circuit is connected to a signal readout pad (notshown) by a wiring 35.

Incidentally, the signal readout part may be configured by CCD and anamplifier, instead of MOS circuits. More specifically, the signalreadout part may be a signal readout part where holes accumulated in thep region 18, p region 20 and p+ region 23 are read into CCD formedinside of the n-type silicon substrate 17 and further transferred to anamplifier by the CCD, and signals according to the holes transferred areoutput from the amplifier.

In this way, the signal readout part includes CCD and CMOS structures,but in view of power consumption, high-speed readout, pixel addition,partial readout and the like, CMOS is preferred.

Incidentally, in FIG. 14, color separation between B light and R lightis effected by color filters 28 and 29, but instead of providing colorfilters 28 and 29, the depth of the pn junction face between the pregion 20 and the n region 21 and the depth of the pn junction facebetween the p region 18 and the n region 19 each may be adjusted toabsorb R light and B light by respective photodiodes. In this case, aninorganic photoelectric conversion part composed of an inorganicmaterial that absorbs light transmitted through the intermediate layer31, generates electric charges according to the light absorbed andaccumulates the electric charges may also be formed between the n-typesilicon substrate 17 and the first electrode layer 30 (for example,between the insulating layer 24 and the n-type silicon substrate 17). Ifthis is the case, an MOS circuit for reading out signals according tothe electric charges accumulated in a charge accumulation region of theinorganic photoelectric conversion part may be provided inside of then-type silicon substrate 17 and a wiring 35 may be connected also tothis MOS circuit.

Also, there may take a construction where one photodiode is providedinside of the n-type silicone substrate 17 and a plurality ofphotoelectric conversion parts are stacked above the n-type siliconsubstrate 17; a construction where a plurality of photodiodes areprovided inside of the n-type silicon substrate 17 and a plurality ofphotoelectric conversion parts are stacked above the n-type siliconsubstrate 17; or when a color image need not be formed, a constructionwhere one photodiode is provided inside of the n-type silicon substrate17 and only one photoelectric conversion part is stacked.

Fifth Embodiment

The solid-state imaging device of this embodiment has a constructionwhere an inorganic layer having the construction shown in FIG. 12described in the third embodiment is not provided but a plurality of(here, three) photoelectric conversion layers are stacked above thesilicon substrate.

FIG. 15 is a schematic cross-sectional view of one pixel portion of asolid-state imaging device for explaining the fifth embodiment of thepresent invention.

The solid-state imaging device 3000 shown in FIG. 15 has a constructionwhere an R photoelectric conversion part containing a first electrodelayer 56, an intermediate layer 57 formed on the first electrode layer56 and a second electrode layer 58 formed on the intermediate layer 57,a B photoelectric conversion part containing a first electrode layer 60,an intermediate layer 61 formed on the first electrode layer 60 and asecond electrode layer 62 formed on the intermediate layer 61, and a Gphotoelectric conversion part containing a first electrode layer 64, anintermediate layer 65 formed on the first electrode layer 64 and asecond electrode layer 66 formed on the intermediate layer 65 arestacked in this order above the silicon substrate 41 in a state of thefirst electrode layer contained in each photoelectric conversion partbeing directed toward the silicon substrate 41 side.

A transparent insulating layer 48 is formed on the silicon substrate 41,the R photoelectric conversion part is formed thereon, a transparentinsulating layer 59 is formed thereon, the B photoelectric conversionpart is formed thereon, a transparent insulating layer 63 is formedthereon, the G photoelectric conversion part is formed thereon, alight-shielding layer 68 having provided therein an opening is formedthereon, and a transparent insulating layer 67 is formed thereon.

The first electrode layer 64, intermediate layer 65 and second electrodelayer 66 contained in the G photoelectric conversion part have the sameconstructions as the first electrode layer 11, intermediate layer 12 andsecond electrode layer 13 shown in FIG. 12, respectively.

The first electrode layer 60, intermediate layer 61 and second electrodelayer 62 contained in the B photoelectric conversion part have the sameconstructions as the first electrode layer 11, intermediate layer 12 andsecond electrode layer 13 shown in FIG. 12, respectively. However, forthe photoelectric conversion layer contained in the intermediate layer61, a material that absorbs blue light and generates an electron and ahole according to the light absorbed is used.

The first electrode layer 56, intermediate layer 57 and second electrodelayer 58 contained in the R photoelectric conversion part have the sameconstructions as the first electrode layer 11, intermediate layer 12 andsecond electrode layer 13 shown in FIG. 12, respectively. However, forthe photoelectric conversion layer contained in the intermediate layer57, a material that absorbs red light and generates an electron and ahole according to the light absorbed is used.

For the electron-blocking layer and hole-blocking layer contained ineach of the intermediate layers 61 and 57, an appropriate material andan appropriate construction are preferably selected so as not to createan energy barrier to the transport of a signal charge, in terms of therelationship between HOMO and LUMO energy levels of each photoelectricconversion layer and HOMO and LUMO energy levels of each blocking layeradjacent thereto.

In the portion light-shielded by the light-shielding layer 68 on thesilicon substrate 41 surface, p+ regions 43, 45 and 47 are formed andthe peripheries of these regions are surrounded by n regions 42, 44 and46, respectively.

The p+ region 43 is electrically connected to the first electrode layer56 via a connection part 54 formed in an opening bored through theinsulating layer 48 and in this region, holes collected at the firstelectrode 56 are accumulated via the connection part 54. The connectionpart 54 is electrically insulated by an insulating layer 51 fromportions except for the first electrode layer 56 and the p+ region 43.

The p+ region 45 is electrically connected to the first electrode layer60 via a connection part 53 formed in an opening bored through theinsulating layer 48, R photoelectric conversion part and insulatinglayer 59 and in this region, holes collected at the first electrodelayer 60 are accumulated via the connection part 53. The connection part53 is electrically insulated by an insulating layer 50 from portionsexcept for the first electrode layer 60 and the p+ region 45.

The p+ region 47 is electrically connected to the first electrode layer64 via a connection part 52 formed in an opening bored through theinsulating layer 48, R photoelectric conversion part, insulating layer59, B photoelectric conversion part and insulating layer 63 and in thisregion, holes collected at the first electrode layer 64 are accumulatedvia the connection part 52. The connection part 52 is electricallyinsulated by an insulating layer 49 from portions except for the firstelectrode layer 64 and the p+ region 47.

The holes accumulated in the p+ region 43 are converted into signalsaccording to the electric charge amount by an MOS circuit comprising ap-channel MOS transistor (not shown) formed inside of the n region 42,the holes accumulated in the p+ region 45 are converted into signalsaccording to the electric charge amount by an MOS circuit comprising ap-channel MOS transistor (not shown) formed inside of the n region 44,the holes accumulated in the p+ region 47 are converted into signalsaccording to the electric charge amount by an MOS circuit comprising ap-channel MOS transistor (not shown) formed inside of the n region 46,and these signals are output to the outside of the solid-state imagingdevice 3000. The MOS circuits above constitute the signal readout partspecified in the scope of claim for patent. Each MOS circuit isconnected to a signal readout pad (not shown) by a wiring 55. Here, thesignal readout part may be configured by CCD and an amplifier, insteadof MOS circuits. More specifically, the signal readout part may be asignal readout part where holes accumulated in the p+ regions 43, 45 and47 are read into CCD formed inside of the silicon substrate 41 andfurther transferred to an amplifier by the CCD, and signals according tothe holes transferred are output from the amplifier.

Incidentally, an inorganic photoelectric conversion part composed of aninorganic material which receives light transmitted through theintermediate layers 57, 61 and 65, generates electric charges accordingto the light received and accumulates the electric charges may also beformed between the silicon substrate 41 and the first electrode layer 56(for example, between the insulating layer 48 and the silicon substrate41). In this case, an MOS circuit for reading out signals according tothe electric charges accumulated in a charge accumulation region of theinorganic photoelectric conversion part may be provided inside of thesilicon substrate 41 and a wiring 55 may be connected also to this MOScircuit.

Such a configuration described in the third and forth embodiments, wherea plurality of photoelectric conversion layers are stacked on a siliconsubstrate, can be realized by the construction shown in FIG. 15.

In these descriptions, the photoelectric conversion layer that absorbs Blight means a photoelectric conversion layer which can absorb at leastlight at a wavelength of 400 to 500 nm and in which the absorption rateat a peak wavelength in the wavelength region above is preferably 50% ormore. The photoelectric conversion layer that absorbs G light means aphotoelectric conversion layer which can absorb at least light at awavelength of 500 to 600 nm and in which the absorption rate at a peakwavelength in the wavelength region above is preferably 50% or more. Thephotoelectric conversion layer that absorbs R light means aphotoelectric conversion layer which can absorb at least light at awavelength of 600 to 700 nm and in which the absorption rate at a peakwavelength in the wavelength region above is preferably 50% or more.

In the case of the construction of the third or fifth embodiment, theremay be considered a pattern where colors are detected in the order suchas BGR, BRG, GBR, GRB, RBG and RGB from the upper layer. Preferably, theuppermost layer is G. In the case of the construction of the fourthembodiment, the combination which can be employed is such a constructionwhere the upper layer is an R layer and the lower layer is BG layers inthe same plane; where the upper layer is a B layer and the lower layeris GR layers in the same plane; or where the upper layer is a G layerand the lower layer is BR layers in the same plane. A construction wherethe upper layer is a G layer and the lower layer is BR layers in thesame plane is preferred.

Sixth Embodiment

FIG. 16 is a schematic cross-sectional diagram of a solid-state imagingdevice for explaining the sixth embodiment of the present invention. InFIG. 16, a cross-section of two pixel portions in a pixel part that is aportion of detecting light and accumulating an electric charge, and across-section of a peripheral circuit part that is a portion where, forexample, wiring connected to an electrode in the pixel part and bondingPAD connected to the wiring are formed, are shown together.

In the pixel part, a p region 421 is formed in the surface area of ann-type silicon substrate 413, an n region 422 is formed in the surfacearea of the p region 421, a p region 423 is formed in the surface areaof the n region 422, and an n region 424 is formed in the surface areaof the p region 423.

The p region 421 accumulates holes of a red (R) componentphotoelectrically converted by a pn junction with the n-type siliconsubstrate 413. A potential change in the p region 421 due toaccumulation of holes of an R component is read out from an MOStransistor 426 formed in the n-type silicon substrate 413 into a signalreadout PAD 427 via a metal wiring 419 connected to the MOS transistor426.

The p region 423 accumulates holes of a blue (B) componentphotoelectrically converted by a pn junction with the n region 422. Apotential change in the p region 423 due to accumulation of holes of a Bcomponent is read out from an MOS transistor 426′ formed in the n region422 into a signal readout PAD 427 via a metal wiring 419 connected tothe MOS transistor 426′.

In the n region 424, a hole accumulation region 425 comprising a pregion that accumulates holes of a green (G) component generated in thephotoelectric conversion layer 123 stacked above the n-type siliconsubstrate 413 is formed. A potential change in the hole accumulationregion 425 due to accumulation of holes of a G component is read outfrom an MOS transistor 426″ formed in the n region 424 into a signalreadout PAD 427 via a metal wiring 419 connected to the MOS transistor426″. Usually, the signal readout PAD 427 is provided for each of thetransistors from which respective color components are read out.

Here, the p region, n region, transistor, metal wiring and others areschematically shown, but the construction and the like of each memberare not limited thereto, and an optimal selection is appropriately madetherefor. Separation between B light and R light is effected by thedepth in the silicon substrate and therefore, for example, selection ofthe depth of pn junction or the like from the silicon substrate surfaceor the dope concentration of each impurity is important. A techniqueused in a normal CMOS image sensor may be applied to the CMOS circuitworking out to a signal readout part. Specifically, a circuitconstruction of reducing the number of transistors in the pixel part,including a low-noise readout column amplifier and a CDS circuit, may beapplied.

A transparent insulating layer 412 comprising silicon oxide, siliconnitride or the like as the main component is formed on the n-typesilicon substrate 413, and a transparent insulating layer 411 comprisingsilicon oxide, silicon nitride or the like as the main component isformed on the insulating layer 412. The thickness of the insulatinglayer 412 is preferably smaller and is 5 μm or less, preferably 3 μm orless, more preferably 2 μm or less, still more preferably 1 μm or less.

Inside of each of insulating layers 411 and 412, a plug 415 comprising,for example, tungsten as the main component and electrically connectingbetween the first electrode layer 414 and the p region 425 as a holeaccumulation region is formed, and the plugs 415 are relayed andconnected by a pad 416 across the insulating layer 411 and theinsulating layer 412. As for the pad 416, a pad comprising aluminum asthe main component is preferably used. Inside of the insulating layer412, the above-described metal wiring 419, gate electrodes for thetransistors 426, 426′ and 426″, and others are also formed. It ispreferred that a barrier layer including the metal wiring is provided.The plug 415 is provided for every one pixel.

Inside of the insulating layer 411, a light-shielding layer 417 isprovided for preventing a noise attributable to generation of anelectric charge by the pn junction between the n region 424 and the pregion 425. As for the light-shielding layer 417, a layer comprisingtungsten, aluminum or the like as the main component is used. Inside ofthe insulating layer 411, a bonding PAD 420 (PAD for externallysupplying a power source) and a signal readout PAD 427 are formed, and ametal wiring (not shown) for electrically connecting between the bondingPAD 420 and the first electrode layer 414 described later is alsoformed.

On the plug 415 for each pixel inside of the insulating layer 411, atransparent first electrode layer 414 is formed. The first electrodelayer 414 is divided for each pixel, and the size thereof determines thelight-receiving area. To the first electrode layer 414, a bias isapplied through the wiring from the bonding PAD 420. A constructionwhere holes can be accumulated in the hole accumulation region 425 byapplying a negative bias to the first electrode 414, with respect to asecond electrode layer 405 which is described later, is preferred.

An intermediate layer 12 having the same structure as in FIG. 12 isformed on the first electrode layer 414, and a second electrode layer405 is formed thereon.

On the second electrode layer 405, a protective layer 404 comprisingsilicon nitride or the like as the main component and having a functionof protecting the intermediate layer 12 is formed. In the protectivelayer 404, an opening is formed at a position not overlapping with thefirst electrode layer 414 of the pixel part. Also, an opening is formedin a part of the insulating layer 411 and the protective layer 404 onthe bonding PAD 420. A wiring 418 comprising aluminum or the like forelectrically connecting between the second electrode layer 405 and thebonding PAD 420, which are exposed by those two openings, and giving apotential to the second electrode layer 405 is formed inside of theopenings as well as on the protective layer 404. As for the material ofthe wiring 418, an aluminum-containing alloy such as Al—Si or Al—Cualloy may also be used.

A protective layer 403 comprising silicon nitride or the like as themain component and protecting the wiring 418 is formed on the wiring418, an infrared-cutting dielectric multilayer layer 402 is formed onthe protective layer 403, and an antireflection layer 401 is formed onthe infrared-cutting dielectric multilayer layer 402.

The first electrode layer 414 fulfills the same function as the firstelectrode layer 11 shown in FIG. 12. The second electrode layer 405fulfills the same function as the second electrode layer 13 shown inFIG. 12.

By such a construction, three BGR color lights can be detected by onepixel to effect color imaging. In the construction of FIG. 16, R and Beach is used as a common value in two pixels, and only the G value isseparately used, but since the sensitivity of G is important inproducing an image, a good color image can be produced even by such aconstruction.

The solid-state imaging device described above can be applied to animaging device including a digital camera, a video camera, a facsimile,a scanner and a copier and can also be utilized as a light sensor suchas biosensor and chemical sensor.

Examples of the material for the insulating layers described in theseembodiments include SiO_(x), Si—N_(x), BSG, PSG, BPSG, a metal oxidesuch as Al₂O₃, MgO, GeO, NiO, CaO, BaO, Fe₂O₃, Y₂O₃ and TiO₂, and ametal fluoride such as MgF₂, LiF, AlF₃ and CaF₂. Among these materials,SiO_(x), SiN_(x), BSG, PSG and BPSG are most preferred.

Incidentally, in the third to sixth embodiments, either a hole or anelectron may be used for reading out signals from portions other thanthe photoelectric conversion layer. More specifically, as describedabove, there may take a construction where holes are accumulated in aninorganic photoelectric conversion part provided between a semiconductorsubstrate and a photoelectric conversion part stacked thereon or in aphotodiode formed inside of the semiconductor substrate and signalsaccording to the holes are read out by a signal readout part, or aconstruction where electrons are accumulated in an inorganicphotoelectric conversion part or a photodiode formed inside of asemiconductor substrate and signals according to the electrons are readout by a signal readout part.

In the third to sixth embodiments, a construction shown in FIG. 13 isused as the photoelectric conversion part provided above the siliconsubstrate, but a construction shown in FIG. 1 and FIGS. 6 to 9 may alsobe used. According to the construction shown in FIG. 13, an electron anda hole can be blocked and therefore, the effect of suppressing a darkcurrent is high. In the case where the electrode opposite the electrodeon the light incident side is used as an electrode for electronextraction, there may take a construction where in FIG. 12, theconnection part 9 is connected to the second electrode 13; where in FIG.14, the connection part 27 is connected to the second electrode 13; orwhere in FIG. 15, the connection part 54 is connected to the secondelectrode 58, the connection part 53 is connected to the secondelectrode 62 and the connection part 52 is connected to the secondelectrode 66.

The solid-state imaging device described in this embodiment has aconstruction where a large number of pixels, one of which is shown inFIGS. 12 to 16, are disposed in an array manner in the same plane andsince RGB color signals can be obtained by this one pixel, this onepixel can be regarded as a photoelectric conversion element thatconverts RGB lights into electric signals. Therefore, the solid-stateimaging device described in this embodiment can be said to have aconstruction where a large number of photoelectric conversion elementsshown in FIGS. 12 to 16 are disposed in an array manner in the sameplane.

Seventh Embodiment

A seventh embodiment where a solid-state imaging device is realized byusing a photoelectric conversion element having a construction shown inFIGS. 17 and 18 is described.

FIG. 17 is a partial surface schematic view of an imaging device forexplaining the embodiment of the present invention, and FIG. 18 is aschematic cross-sectional view cut along the A-A line of the imagingdevice shown in FIG. 17. In FIG. 17, illustration of a microlens 14 isomitted.

A p-well layer 2 is formed on an n-type silicon substrate 1. In thefollowing, the n-type silicon substrate 1 and the p-well layer 2 arecollectively referred to as a semiconductor substrate. In the rowdirection and the column direction crossing with the row direction atright angles in the same plane above the semiconductor substrate, threekinds of color filters, that is, a color filter 13 r mainly transmittingR light, a color filter 13 g mainly transmitting G light, and a colorfilter 13 b mainly transmitting B light, each is numerously arrayed.

As for the color filter 13 r, a known material that transmits R lightmay be used. As for the color filter 13 g, a known material thattransmits G light may be used. As for the color filter 13 b, a knownmaterial that transmits B light may be used.

As for the array of color filters 13 r, 13 g and 13 b, a color filterarray used in known single-plate solid-state imaging devices (e.g.,Bayer array, longitudinal stripe, lateral stripe) may be employed.

A transparent electrode 11 r is formed above an n region 4 r, atransparent electrode 11 g is formed above an n region 4 g, and atransparent electrode 11 b is formed above an n region 4 b. Thetransparent electrodes 11 r, 11 g and 11 b are divided to correspond tothe color filters 13 r, 13 g and 13 b, respectively. The transparentelectrodes 11 r, 11 g and 11 b each has the same function as the lowerelectrode 11 of FIG. 1.

A photoelectric conversion layer 12 in one-sheet construction shared incommon among the color filters 13 r, 13 g and 13 b is formed on thetransparent electrodes 11 r, 11 g and 11 b.

An upper electrode 13 in one-sheet construction shared in common amongthe color filters 13 r, 13 g and 13 b is formed on the photoelectricconversion layer 12.

A photoelectric conversion element corresponding to the color filter 13r is formed by the transparent electrode 11 r, the opposing upperelectrode 13, and a part of the photoelectric conversion layer 12sandwiched therebetween. This photoelectric conversion element ishereinafter referred to as an R photoelectric conversion element,because this element is formed on a semiconductor substrate.

A photoelectric conversion element corresponding to the color filter 13g is formed by the transparent electrode 11 g, the upper electrode 13opposing it, and a part of the photoelectric conversion layer 12sandwiched therebetween. This photoelectric conversion element ishereinafter referred to as a G photoelectric conversion element.

A photoelectric conversion element corresponding to the color filter 13b is formed by the transparent electrode 11 b, the upper electrode 13opposing it, and a part of the photoelectric conversion layer 12sandwiched therebetween. This photoelectric conversion element ishereinafter referred to as a B photoelectric conversion element.

In the n region inside of the p-well layer 2, a high-concentrationn-type impurity region (hereinafter referred to as an “n+ region”) 4 rfor accumulating an electric charge generated in the photoelectricconversion layer 12 of the on-substrate R photoelectric conversionelement is formed. Incidentally, a light-shielding layer is preferablyprovided on the n+ region 4 r for preventing light from entering the n+region 4 r.

In the n region inside of the p-well layer 2, an n+ region 4 g foraccumulating an electric charge generated in the photoelectricconversion layer 12 of the on-substrate G photoelectric conversionelement is formed. Incidentally, a light-shielding layer is preferablyprovided on the n+ region 4 g for preventing light from entering the n+region 4 g.

In the n region inside of the p-well layer 2, an n+ region 4 b foraccumulating an electric charge generated in the photoelectricconversion layer 12 of the on-substrate B photoelectric conversionelement is formed. Incidentally, a light-shielding layer is preferablyprovided on the n+ region 4 b for preventing light from entering the n+region 4 b.

A contact part 6 r comprising a metal such as aluminum is formed on then+ region 4 r, the transparent electrode 11 r is formed on the contactpart 6 r, and the n+ region 4 r and the transparent electrode 11 r areelectrically connected by the contact part 6 r. The contact part 6 r isembedded in an insulating layer 5 transparent to visible light andinfrared light.

A contact part 6 g comprising a metal such as aluminum is formed on then+ region 4 g, the transparent electrode 11 g is formed on the contactpart 6 g, and the n+ region 4 g and the transparent electrode 11 g areelectrically connected by the contact part 6 g. The contact part 6 g isembedded in the insulating layer 5.

A contact part 6 b comprising a metal such as aluminum is formed on then+ region 4 b, the transparent electrode 11 b is formed on the contactpart 6 b, and the n+ region 4 b and the transparent electrode 11 b areelectrically connected by the contact part 6 b. The contact part 6 b isembedded in the insulating layer 5.

Inside of the p-well layer 2, in the region other than those where then+ regions 4 r, 4 g and 4 b are formed, a signal readout part 5 r forreading out signals according to electric charges generated in the Rphotoelectric conversion element and accumulated in the n+ region 4 r, asignal readout part 5 g for reading out signals according to electriccharges generated in the G photoelectric conversion element andaccumulated in the n+ region 4 g, and a signal readout part 5 b forreading out signals according to electric charges generated in the Bphotoelectric conversion element and accumulated in the n+ region 4 bare formed. For each of the signal readout parts 5 r, 5 g and 5 b, aknown construction using a CCD or MOS circuit may be employed.Incidentally, a light-shielding layer is preferably provided on thesignal readout parts 5 r, 5 g and 5 b for preventing light from enteringthe signal readout parts 5 r, 5 g and 5 b.

FIG. 19 is a view showing a specific construction example of the signalreadout part 5 r shown in FIG. 18. In FIG. 19, the same constituents asthose in FIGS. 17 and 18 are denoted by like numerical references.Incidentally, the signal readout parts 5 r, 5 g and 5 b have the sameconstruction and the description of the signal readout parts 5 g and 5 bis omitted.

The signal readout part 5 r comprises a reset transistor 543 with adrain being connected to the n+ region 4 r and a source being connectedto a power source Vn, an output transistor 542 with a gate beingconnected to the drain of the reset transistor 543 and a source beingconnected to a power source Vcc, a row selection transistor 541 with asource being connected to the drain of the output transistor 542 and adrain being connected to a signal output line 545, a reset transistor546 with a drain being connected to the n region 3 r and a source beingconnected to a power source Vn, an output transistor 547 with a gatebeing connected to the drain of the reset transistor 546 and a sourcebeing connected to a power source Vcc, and a row selection transistor548 with a source being connected to the drain of the output transistor547 and a drain being connected to a signal output line 549.

When a bias voltage is applied between the transparent electrode 11 rand the upper electrode 13, an electric charge is generated according tolight incident into the photoelectric conversion layer 12 and theelectric charge moves to the n+ region 4 r through the transparentelectrode 11 r. Electric charges accumulated in the n+ region 4 r areconverted by the output transistor 542 into signals according to theelectric charge amount. Here, when the row selection transistor 541 isturned ON, the signals are output to the signal output line 545. Afterthe output of signals, the electric charge inside of the n+ region 4 ris reset by the reset transistor 543.

In this way, the signal readout part 5 r can be constructed by a knownMOS circuit comprising three transistors.

Backing to FIG. 18, protective layers 15 and 16 constituting a two-layerstructure for protecting the photoelectric conversion elements on thesubstrate are formed on the photoelectric conversion layer 12, and colorfilters 13 r, 13 g and 13 b are formed on the protective layer 16.

This imaging device 100 is produced by forming the photoelectricconversion layer 12 and then forming the color filters 13 r, 13 g and 13b, and the like, but the formation of color filters 13 r, 13 g and 13 binvolves a photolithography step or a baking step and in the case ofusing an organic material as the photoelectric conversion layer 12, whenthe photolithography step or baking step is performed in the state ofthe photoelectric conversion layer 12 being exposed, this causesdeterioration in the properties of the photoelectric conversion layer12. In the imaging device 100, the protective layers 15 and 16 areprovided for preventing the properties of the photoelectric conversionlayer 12 from deterioration ascribable to such a production process.

The protective layer 15 is preferably an inorganic layer comprising aninorganic material and being formed by an ALCVD method. The ALCVD methodis an atomic layer CVD method and enables the formation of a denseinorganic layer, and the layer formed can work out to an effectiveprotective layer of the photoelectric conversion layer 9. The ALCVDmethod is also known as an ALE method or an ALD method. The inorganiclayer formed by the ALCVD method preferably comprises Al₂O₃, SiO₂, TiO₂,ZrO₂, MgO, HfO₂ or Ta₂O₅, more preferably Al₂O₃ or SiO₂, and mostpreferably Al₂O₃.

The protective layer 16 is formed on the protective layer 15 for moreenhancing the performance of protecting the photoelectric conversionlayer 12 and is preferably an organic layer comprising an organicpolymer. The organic polymer is preferably parylene, more preferablyparylene C. Incidentally, the protective layer 16 may be omitted, or thearrangement of the protective layer 15 and the protective layer 16 maybe reversed. A high effect of protecting the photoelectric conversionlayer 12 is obtained particularly by the construction shown in FIG. 18.

When a predetermined bias voltage is applied to the transparentelectrode 11 r and the upper electrode 13, the electric charge generatedin the photoelectric conversion layer 12 constituting the on-substrate Rphotoelectric conversion element moves to the n+ region 4 r through thetransparent electrode 11 r and the contact part 6 r and is accumulatedin the region. Signals according to electric charges accumulated in then+ region 4 r are read out by the signal readout part 5 r and outputoutside of the imaging device 100.

Similarly, when a predetermined bias voltage is applied to thetransparent electrode 11 g and the upper electrode 13, the electriccharge generated in the photoelectric conversion layer 12 constitutingthe on-substrate G photoelectric conversion element moves to the n+region 4 g through the transparent electrode 11 g and the contact part 6g and is accumulated therein. Signals according to electric chargesaccumulated in the n+ region 4 g are read out by the signal readout part5 g and output outside of the imaging device 100.

Also, similarly, when a predetermined bias voltage is applied to thetransparent electrode 11 b and the upper electrode 13, the electriccharge generated in the photoelectric conversion layer 12 constitutingthe on-substrate B photoelectric conversion element moves to the n+region 4 b through the transparent electrode 11 b and the contact part 6b and is accumulated therein. Signals according to electric chargesaccumulated in the n+ region 4 b are read out by the signal readout part5 b and output outside of the imaging device 100.

In this way, the imaging device 100 can output, to the exterior, thesignal of an R component according to the electric charge generated inthe R photoelectric conversion element, the signal of a G componentaccording to the electric charge generated in the G photoelectricconversion element, and the signal of a B component according to theelectric charge generated in the B photoelectric conversion element,whereby a color image can be obtained. By this form, the photoelectricconversion part becomes thin, so that resolution can be enhanced and afalse color can be reduced. Also, the opening ratio can be made largeirrespective of the lower circuit and therefore, high sensitivity can beachieved. Furthermore, a microlens can be omitted and this is effectivein reducing the number of components.

In this embodiment, the organic photoelectric conversion layer needs tohave a maximum absorption wavelength in the green light region and anabsorption region over the entire visible light, but this can bepreferably realized by the materials specified above.

In the above, an embodiment using the photoelectric conversion elementof the present invention as an imaging device is described, but thephotoelectric conversion element of the present invention shows highphotoelectric conversion efficiency and therefore, exhibits highperformance also when used as a solar cell.

As for the preferred device construction in use as a solar cell, inaddition to the constructions according to the present invention, acombination of the photoelectric conversion material described in thepresent invention with a construction described, for example, non-patentdocument (Adv. Mater., 17, 66 (2005)) may be applied.

Synthesis examples of the compounds used in the present invention aredescribed below.

D-105 is DCTP described in Chem. Mater, Vol. 13, pp. 456-458 (2001) andwas synthesized by referring to this paper.

Compound D-100 was synthesized by using 2,6-dimethyl-γ-pyrone in placeof Raw Material C in Compound 1 described in JP-A-2000-351774.

Compound D-1 was synthesized by using 2,6-dimethyl-γ-pyrone in place ofRaw Material C and 1,3-indanedione in place of Raw material e inCompound 1 described in JP-A-2000-351774.

The present invention is described in greater detail below by referringto Examples, but the present invention is of course not limited to theseExamples.

EXAMPLE 1

In the configuration of FIG. 12, amorphous ITO of 30 nm was layer-formedon a CMOS substrate by sputtering, and a pixel electrode 11 was formedthrough patterning by photolithography such that one pixel was presenton a photodiode (PD) on the CMOS substrate. Thereon, layers obtained bydeposition of EB-3 in 100 nm and co-deposition of D-105 and fullerene(C₆₀) in 100 nm and 200 nm, respectively, in terms of a single layer,were layer-formed by vacuum heating vapor deposition to form aphotoelectric conversion layer 12, and amorphous ITO was furtherlayer-formed as an upper electrode to a thickness of 5 nm by sputteringto form a transparent electrode 13, whereby a solid-state imaging devicewas produced. The vacuum vapor deposition of the photoelectricconversion layer 12 was performed at a vacuum degree of 4×10⁻⁴ Pa orless for all layers.

EXAMPLE 2

A solid-state imaging device was produced in the same manner except thatin Example 1, D-105 of the photoelectric conversion layer 12 was changedto D-1.

COMPARATIVE EXAMPLE 1

A solid-state imaging device was produced in the same manner except thatin Example 1, the photoelectric conversion layer 12 was changed to alayer obtained by layer-forming D-105 alone to a thickness of 100 nm.

COMPARATIVE EXAMPLE 2

A solid-state imaging device was produced in the same manner except thatin Comparative Example 1, D-105 was changed to D-1.

The external quantum efficiency at a wavelength of maximum sensitivityat a dark current of 400 pA/cm² and the relative response speed of eachof the photoelectric conversion elements produced in Examples 1 and 2and Comparative Examples 1 and 2 are shown in Table A. Incidentally,when measuring the photoelectric conversion performance of each device,an appropriate voltage was applied.

TABLE A External Quantum Efficiency at Compound Used for Wavelength ofMaximum Light Absorption Sensitivity at Dark Current of Rising Time from0 to and Photoelectric 400 pA/cm² 98% Signal Strength Conversion(relative value) (relative value) Example 1 D-105 and C₆₀ 100 1 Example2 D-1 and C₆₀ 66 1 Comparative D-105 6 100 Example 1 Comparative D-1 9100 Example 2

As seen from Table A, according to the present invention, imaging can beperformed at a high response speed and a high S/N.

EXAMPLE 3

On a patterned ITO electrode, layers obtained by co-deposition of D-105and fullerene (C₆₀) to a thickness of 50 nm and 50 nm, respectively, interms of a single layer were layer-formed by vacuum heating vapordeposition to form a photoelectric conversion layer, and an Al electrodewas layer formed thereon to a thickness of 100 nm by vacuum vapordeposition. The obtained device was measured for the solar cellcharacteristics under the irradiation condition of AM 1.5100 mW/cm², asa result, the short-circuit current value was 2.2 mA/cm², the openvoltage was 0.16 V, the fill factor was 0.28, and the energy conversionefficiency was 0.10%.

A photoelectric conversion element according to an exemplary embodimentof the invention can be applied as a solid-state imaging device to animaging device such as a digital camera, a video camera, a facsimile, ascanner, and a copier. Further, it is usable as a photodetector such asa biosensor or a chemical sensor.

1. A photoelectric conversion element comprising: an electricallyconductive thin layer, an organic photoelectric conversion layer, and atransparent electrically conductive thin layer, wherein the organicphotoelectric conversion layer contains a compound having a partialstructure represented by formula (I) and a fullerene or a fullerenederivative:

wherein X represents O, S or N—R₁₀, and R₁₀ represents a hydrogen atomor a substituent; R^(x) and R^(y) each independently represents ahydrogen atom or a substituent, at least one of R^(x) and R^(y)represents an electron-withdrawing group, and R^(x) and R^(y) maycombine to form a ring; R represents a bond, a hydrogen atom or asubstituent, and at least one R is a bond; nr represents an integer of 1to 4, R's may be the same or different when nr is 2 or more, and R's atthe 2- and 3-positions or R's at the 5- and 6-positions may combine witheach other to form a ring.
 2. The photoelectric conversion elementaccording to claim 1, wherein X is O.
 3. The photoelectric conversionelement according to claim 1, wherein the compound is represented byformula (III):

wherein X represents O, S or N—R₁₀, and R₁₀ represents a hydrogen atomor a substituent; R^(x) and R^(y) each independently represents ahydrogen atom or a substituent, at least one of R^(x) and R^(y)represents an electron-withdrawing group, and R^(x) and R^(y) maycombine to form a ring; R₂₁, R₂₂ and R₂₃ each independently represents ahydrogen atom or a substituent, and R₂₁ and R₂₂ may combine with eachother to form a ring; L₁ and L₂ each independently represents a methinegroup or a substituted methine group; n1 represents an integer of 1 ormore; and R₂₄ to R₃₇ each independently represents a hydrogen atom or asubstituent, and two of R₂₄ to R₃₇ may combine with each other to form aring.
 4. The photoelectric conversion element according to claim 3,wherein R₂₂ and R₂₃ both are a hydrogen atom.
 5. The photoelectricconversion element according to claim 3, wherein L₁ and L₂ both are anunsubstituted methine group.
 6. The photoelectric conversion elementaccording to claim 3, wherein n1 is
 1. 7. The photoelectric conversionelement according to claim 3, wherein R₂₄ to R₃₇ each is a hydrogenatom.
 8. The photoelectric conversion element according to claims 3,wherein X is O.
 9. The photoelectric conversion element according toclaim 1, wherein the fullerene is C₆₀.
 10. The photoelectric conversionelement according to claim 1, wherein the organic photoelectricconversion layer has a bulk-heterostructure formed in a state of thecompound and a fullerene or a fullerene derivative being mixed.
 11. Thephotoelectric conversion element according to claim 1, wherein the ratioof the fullerene or the fullerene derivative to the compound is 50% bymol or more.
 12. The photoelectric conversion element according to claim1, wherein the organic photoelectric conversion layer is formed by avacuum vapor deposition method.
 13. The photoelectric conversion elementaccording to claim 1, wherein the transparent electrically conductivethin layer is an electrode layer from above which light is incident intothe organic photoelectric conversion layer.
 14. The photoelectricconversion element according to claim 13, wherein the transparentelectrically conductive thin layer includes a transparent electricallyconductive oxide.
 15. The photoelectric conversion element according toclaim 1, wherein the transparent electrically conductive thin layer isformed directly on the organic photoelectric conversion layer.
 16. Thephotoelectric conversion element according to claim 15, wherein anelectric field of 10⁻⁴ V/cm to 1×10⁷ V/cm is applied between electrodesof the photoelectric conversion element.
 17. The photoelectricconversion element according to claim 1, wherein the electricallyconductive thin layer, the organic photoelectric conversion layer, andthe transparent electrically conductive thin layer are stacked in thisorder.
 18. An imaging device comprising a photoelectric conversionelement according to claim 1.